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Garrett GT4088R with fitment issues

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Old 07-13-17, 06:56 PM
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Garrett GT4088R with fitment issues

Gentlemen, I need some help. Here's the deal; I am tackling some projects right now and have decided that I have to get a turbo blanket onto my setup. I found my wheel speed sensor wiring for example burned to glass almost because my the turbine housing is within a couple mm's of the frame.

My solution was to shave a touch off the manifold flange and maybe the turbo flange as well to give me some more clearance on that side. Problem is, if I do that it will bring the turbo in and most probably make the compressor housing hit the LIM.

So, I'm in a classic "damned if you do, damned if you don't" scenario and I don't know what to do exactly.

Here's my options as I see it:

1: Remove turbo and manifold and beat the strut tower in slightly to give me the requisite space for the blanket to fit around the turbine housing. The fear is doing damage to the strut tower which would weaken it and compromise the structural integrity of the strut tower.

2: Shave a few mm's off the manifold flange and maybe turbo flange, and then sand down or machine material off the LIM and hope you can remove enough material without breaking through into the intake runner.

3: Replace turbine housing with a .85 A/R housing which I've confirmed with ATP Turbo is about 2mm shorter from flange to the apex of the turbine housing, than my .95 A/R turbine housing currently on the car. This makes the most sense but is most expensive at $300-$400 for the housing.

4: Ditch the turbo, try to sell it and buy a smaller turbo better suited for the setup for equal or lesser money. This would most probably take time and my car is down right now. I don't want it to sit too long for obvious reasons.

Your feedback would be appreciated fellas.

Nick
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Old 07-13-17, 09:04 PM
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MJ said it best, just beat it.


You can also use a stainless steel heat shield aka pot.
Inconel heat shield, also costly.

But both are way thinner.

I don't have pictures but I also run a GT40 w/ a 1.06 hotside. XS/HKS manifold. Didn't have to beat the strut tower, but the areas around there. Ran a blanket for years, switched to inconel, loads of rooom.
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Old 07-13-17, 09:19 PM
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silentblu, thanks for your feedback dude. My manifold is from A-Spec and I believe they basically didn't want to re-engineer their GT35 manifold or something and made this work. The position of the turbo is far from ideal. Check out these pictures:



Notice how the compressor housing is nearly touching the LIM in two spots.



And here, you can see the turbine housing is virtually touching the strut tower. If I pull a Michael, I'll have to beat in the corner of the strut tower possibly weakening it. That's my dilemma.

I thought about running this inconel shield, but at $520 and no guarantee it would actually fit, I think I'm not going to fuss with it...





Im leaning towards buying the .85 turbine housing, seeing where I'm at and then resorting to violence if necessary. If I gain a little bit of clearance from the smaller housing, perhaps I'll only have to dent the strut tower, as opposed to beating the hell out of it.

Nick

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Old 07-14-17, 09:39 AM
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Get the housing ceramic coated.
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Old 07-14-17, 01:17 PM
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Originally Posted by Shainiac View Post
Get the housing ceramic coated.
That would definitely represent the easiest route, no question. However, ceramic coating has it's limitations. I know turbo blankets are so effective at mitigating heat from the turbine housing that you can actually rest your hand on the blanket while doing a pull on the dyno and not burn your hand. I wouldn't dream of doing that with a ceramic coated turbine housing.

My goal is to reduce the temperatures in that area to the point where I don't need to treat the AC lines in that area, or the coolant hoses. With Titanium heat wrap and the Titanium turbo blanket, I think I can achieve that goal.

Nick
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Old 07-14-17, 06:28 PM
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From your pictures it looks very similar to my setup location wise, I sit farther back towards the firewall, my compressor is approximately where your exhaust housing would be.
I was able to fit various turbo blankets, while the engine/turbo was in the car. The square-ish PTP looking ones, and then the rounder titanium looking ones. Both were pretty much sandwiched to the frame, and I consider all turbo blankets single use, as in you install it once, and if you take it off its done, all the fiberglass/material flakes off/crispy. It did reduce temps but I would not rest my hand during a pull on them.

I would recommend you contact Turblown, they do Inconel wraps and are slightly cheaper then the one you quoted ~$450 (?), and will have you send in your exhaust housing to get fit. They will likely be able to provide you more details on thickness and fitment. I had mine done locally in CA.

Is the exhaust housing touching the frame in the last picture? or is that just from the angle?
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Old 07-14-17, 06:45 PM
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Originally Posted by silentblu View Post
From your pictures it looks very similar to my setup location wise, I sit farther back towards the firewall, my compressor is approximately where your exhaust housing would be.
I was able to fit various turbo blankets, while the engine/turbo was in the car. The square-ish PTP looking ones, and then the rounder titanium looking ones. Both were pretty much sandwiched to the frame, and I consider all turbo blankets single use, as in you install it once, and if you take it off its done, all the fiberglass/material flakes off/crispy. It did reduce temps but I would not rest my hand during a pull on them.

I would recommend you contact Turblown, they do Inconel wraps and are slightly cheaper then the one you quoted ~$450 (?), and will have you send in your exhaust housing to get fit. They will likely be able to provide you more details on thickness and fitment. I had mine done locally in CA.

Is the exhaust housing touching the frame in the last picture? or is that just from the angle?
I spoke with Elliot at Turblown and he quoted me $550 to custom make an inconel shield. At this stage I'm basically between two options: either hammer the strut tower and be done, or spend $300 on a .85 a/r turbine housing which is smaller and hope that works, and maybe still have to bang the strut tower.

My only option that doesn't include
modifying the strut tower is to shave the manifold flange to bring it further in which may then introduce the compressor housing to the LIM. There's only a few millimeters between the compressor and LIM as is, so if I take material off the flange and pull the turbo in towards the engine, I'll definitely have to start shaving the LIM to make it work.

And no, that last picture looks like it is; EXTREMELY close. There's about 1mm gap between the turbine housing and strut tower. The "frame rail" portion of the body has a little bigger of a gap.

Nick
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Old 07-14-17, 07:38 PM
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I have no real input, other than I luv me them LIM passthrough caps. Just screams 'PRO.'

Best of luck to you Stranger
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Old 07-15-17, 01:32 AM
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Originally Posted by GoodfellaFD3S View Post
I have no real input, other than I luv me them LIM passthrough caps. Just screams 'PRO.'

Best of luck to you Stranger
lmao! Rich, we've already been through this man, the previous owner put them things on. You wait till the after! Don't critique the before...

Nick
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Old 07-16-17, 05:07 AM
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Originally Posted by Brilliant7-LFC View Post
I spoke with Elliot at Turblown and he quoted me $550 to custom make an inconel shield. At this stage I'm basically between two options: either hammer the strut tower and be done, or spend $300 on a .85 a/r turbine housing which is smaller and hope that works, and maybe still have to bang the strut tower.

My only option that doesn't include
modifying the strut tower is to shave the manifold flange to bring it further in which may then introduce the compressor housing to the LIM. There's only a few millimeters between the compressor and LIM as is, so if I take material off the flange and pull the turbo in towards the engine, I'll definitely have to start shaving the LIM to make it work.

And no, that last picture looks like it is; EXTREMELY close. There's about 1mm gap between the turbine housing and strut tower. The "frame rail" portion of the body has a little bigger of a gap.

Nick
If it is extremely close, I highly doubt a turbo blanket would fit even with the smaller AR housing. If you have seen how thick an inconel shield is vs. any blanket, you will understand why. The inconel shield itself is also pliable. Not exact figures, but the blanket will be anywhere from 1/8" to 1/4" maybe, and the inconel is a sheet of metal 16/18 gauge in thickness, no more then 1/16".
For proper heat management, you need that air gap to act as an insulator, direct contact for all heat management products have a much lower rated temperature rating, and a smashed turbo blanket will likely get extra crispy extra fast.

Did Elliot say anything on the thickness or the likely outcome with going inconel?

Have you thought or are you prepared with the other aspects of going with a smaller AR exhaust housing? Need for tune, powerband of the car, future aspirations? i.e. more boost? etc.

Think about it, Inconel $550 vs. new housing ($300), turbo blanket ($100) and a tune (???). My math puts the inconel as winning.

OR leave the housing alone, and shield everything else. LIM, AC lines, box in your air filter, wrap your downpipe.
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Old 07-16-17, 09:16 AM
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From talking to Nick extensively on this subject, one thing he really liked about the blankets is that you can rest your hand on it and not get burned. I've been using inconel on my manifolds and turbine housings for many years now....... and I wouldn't dream of resting my hand on it after use, it would not be fun

Inconel with the air gap is the way to go as it doesn't smother the turbine, but you'd still want to shield all the peripheral parts around it as you still get a degree of radiant heat.
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Old 07-16-17, 10:23 AM
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Originally Posted by silentblu View Post
If it is extremely close, I highly doubt a turbo blanket would fit even with the smaller AR housing. If you have seen how thick an inconel shield is vs. any blanket, you will understand why. The inconel shield itself is also pliable. Not exact figures, but the blanket will be anywhere from 1/8" to 1/4" maybe, and the inconel is a sheet of metal 16/18 gauge in thickness, no more then 1/16".
For proper heat management, you need that air gap to act as an insulator, direct contact for all heat management products have a much lower rated temperature rating, and a smashed turbo blanket will likely get extra crispy extra fast.

Did Elliot say anything on the thickness or the likely outcome with going inconel?

Have you thought or are you prepared with the other aspects of going with a smaller AR exhaust housing? Need for tune, powerband of the car, future aspirations? i.e. more boost? etc.

Think about it, Inconel $550 vs. new housing ($300), turbo blanket ($100) and a tune (???). My math puts the inconel as winning.

OR leave the housing alone, and shield everything else. LIM, AC lines, box in your air filter, wrap your downpipe.
All valid points. Yes, I have considered all the points you mentioned. I was already in the middle of changing my intercooler and fuel rails/injectors when I stupidly decided to take this on, so I will be getting a retune regardless. Inconel is attractive, but as pointed out; if I don't have the air gap, it effectiveness is reduced. The material itself is extremely thin but if the airgap is negated the materials effectiveness is almost non existent. I feel that with the blanket the airgap in a sense exists in the thickness of the blanket and doesn't rely on the shield being a certain distance from the metal surface of the housing. Meaning, if you have a really snug fit turbo blanket, it's effectiveness isn't compromised. Yet, if your inconel shield were touching the housing, it'd likely be just as hot as the housing itself.

The performance changes of going with a .85 housing are something I've considered as well. My turbo as it sits with the .95 housing is pretty laggy. I have a short runner manifold and twin scroll setup, divided T4. Reducing the housing to .85 should "wake up" the turbo a bit. I actually sent a PM to Howard on the subject to get some input on the smaller housing's effect in a mathematical sense, but I haven't heard back.

Originally Posted by GoodfellaFD3S View Post
From talking to Nick extensively on this subject, one thing he really liked about the blankets is that you can rest your hand on it and not get burned. I've been using inconel on my manifolds and turbine housings for many years now....... and I wouldn't dream of resting my hand on it after use, it would not be fun

Inconel with the air gap is the way to go as it doesn't smother the turbine, but you'd still want to shield all the peripheral parts around it as you still get a degree of radiant heat.
Yes, Rich is right, I've mentioned that quite a bit lol - I state that not because I wish to place my hand on my blanket during a session, but it proves to me the effectiveness of the blanket. We all know how hot these turbos get and having that extreme level of protection when my setup in particular is so close to the LIM, is very reassuring.

Nick
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Old 07-17-17, 07:07 AM
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Originally Posted by Brilliant7-LFC View Post
Gentlemen, I need some help. Here's the deal; I am tackling some projects right now and have decided that I have to get a turbo blanket onto my setup. I found my wheel speed sensor wiring for example burned to glass almost because my the turbine housing is within a couple mm's of the frame.

My solution was to shave a touch off the manifold flange and maybe the turbo flange as well to give me some more clearance on that side. Problem is, if I do that it will bring the turbo in and most probably make the compressor housing hit the LIM.

So, I'm in a classic "damned if you do, damned if you don't" scenario and I don't know what to do exactly.

Here's my options as I see it:

1: Remove turbo and manifold and beat the strut tower in slightly to give me the requisite space for the blanket to fit around the turbine housing. The fear is doing damage to the strut tower which would weaken it and compromise the structural integrity of the strut tower.

2: Shave a few mm's off the manifold flange and maybe turbo flange, and then sand down or machine material off the LIM and hope you can remove enough material without breaking through into the intake runner.

3: Replace turbine housing with a .85 A/R housing which I've confirmed with ATP Turbo is about 2mm shorter from flange to the apex of the turbine housing, than my .95 A/R turbine housing currently on the car. This makes the most sense but is most expensive at $300-$400 for the housing.

4: Ditch the turbo, try to sell it and buy a smaller turbo better suited for the setup for equal or lesser money. This would most probably take time and my car is down right now. I don't want it to sit too long for obvious reasons.

Your feedback would be appreciated fellas.

Nick
Nick,

I vote for #3 or #4, I had a similar issue, but it was the other way around, the turbo hot side was hitting the intake manifold (more like the intake manifold was in the turbo's way). I ended up making a spacer...

Spend money on something that you could sell in the future, and gain some of your expenses back. In my case, nobody wants a custom adapter, on the other hand, selling a turbine housing will sell fairly easy.

Yes a turbo blanket will shorten the life of your turbine housing, that's a fact that I accept, in order to keep under hood temps "under control".

Try a turbo blanket before doing anything, even with the lack of space between the turbine housing and the strut tower/LIM, you should be able to fit it. A blanket is the cheapest solution, the easiest, and quite frankly, the one that will provide the best results.
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Old 07-18-17, 11:55 AM
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I'm with option 4. Do you really need such a large frame turbo to meet your goals?
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Old 07-18-17, 03:14 PM
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Originally Posted by arghx View Post
I'm with option 4. Do you really need such a large frame turbo to meet your goals?
The simple answer is: probably not?

I put the question mark because I don't really know. I reached out to Howard Coleman because I know he often times does the math on turbo's and seems to know my turbo well. I spoke with him when I first got the car to discuss some other things and he spoke highly of the GT4088R, so I figured he wouldn't steer me wrong...long story, short -- Howard's exact words were:

"the tail could be wagging the dog here and you will be creating a larger problem.
do not go anywhere near the smaller hotside. it will produce too much exhaust backpressure and eventual detonation.

the proper hotside is the 1.06 but the .95 will work. the cause of your problem is the manifold not the turbo of course. i would not hesitate to "modify" my shock tower/inner fender to fit the turbo but that is just me. engineer first and aesthetics later."


With that sort of advice, I decided against the .85 turbine housing and beat the hell out of my strut tower yesterday. I've cleared enough space now to fit the blanket - I think. We will see in a couple week's time when I get the blanket.

At first, I thought the smaller hotside would be a good idea, in order to reduce my lag somewhat. But, after doing some research and getting that advice from Howard, I've opted to make a couple changes first before considering going that route.

First, I've increased my spring pressure on the gate from 7psi to 14psi. I will also reference boost to the WG from the compressor housing, as that's how the diagram in the TurboSmart manual says to do it. Perhaps with those changes, I'll see a reduction in lag from the turbo.

I'm open to other suggestions as well...

Thanks guys!

Nick
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Old 07-19-17, 07:18 AM
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Originally Posted by Brilliant7-LFC View Post
The simple answer is: probably not?

I put the question mark because I don't really know. I reached out to Howard Coleman because I know he often times does the math on turbo's and seems to know my turbo well. I spoke with him when I first got the car to discuss some other things and he spoke highly of the GT4088R, so I figured he wouldn't steer me wrong...long story, short -- Howard's exact words were:

"the tail could be wagging the dog here and you will be creating a larger problem.
do not go anywhere near the smaller hotside. it will produce too much exhaust backpressure and eventual detonation.

the proper hotside is the 1.06 but the .95 will work. the cause of your problem is the manifold not the turbo of course. i would not hesitate to "modify" my shock tower/inner fender to fit the turbo but that is just me. engineer first and aesthetics later."


With that sort of advice, I decided against the .85 turbine housing and beat the hell out of my strut tower yesterday. I've cleared enough space now to fit the blanket - I think. We will see in a couple week's time when I get the blanket.

At first, I thought the smaller hotside would be a good idea, in order to reduce my lag somewhat. But, after doing some research and getting that advice from Howard, I've opted to make a couple changes first before considering going that route.

First, I've increased my spring pressure on the gate from 7psi to 14psi. I will also reference boost to the WG from the compressor housing, as that's how the diagram in the TurboSmart manual says to do it. Perhaps with those changes, I'll see a reduction in lag from the turbo.

I'm open to other suggestions as well...

Thanks guys!

Nick
DAMN, you should've test fitted the blanket BEFORE hammering the strut tower

For what is worth, I run a T4 .84 housing, been doing it for 5 years or so, no issues; however my car was tuned by an experience tuner, AND I run water injection on to of the tune AND I only run 15psi on a T04S
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Old 07-19-17, 11:55 AM
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Originally Posted by KNONFS View Post
DAMN, you should've test fitted the blanket BEFORE hammering the strut tower

For what is worth, I run a T4 .84 housing, been doing it for 5 years or so, no issues; however my car was tuned by an experience tuner, AND I run water injection on to of the tune AND I only run 15psi on a T04S
Dude, there was absolutely no way that blanket was gonna fit. I'm gonna prep the metal for paint and put down some gloss black hi temp paint to prevent any rusting and call it a day. One day down the road I will have to paint the car anyway, so when that happens, this will all just be a memory. I'm thinking a Ferrari red or yellow by the way...

In any event, the deed is done and there's no going back now my friend. I am certain that a .85 housing wouldn't have caused my engine to blow up, but the gains can't be measured. I couldn't find any good information to help me make the "right" decision. All I had to work with was the opinion of Howard, which I value - and the understanding that rotary's typically have higher demand for flow to keep it safe and make the power you want.

Plus, the cost was a factor. This project started as a re-tooling of my fuel system to incorporate my CJM rails and larger primary injectors, a new intercooler and a retune. My original budget for this was about $1,000. After this is all said and done, this project will more than likely cost me 50% more than that and spending another $300 on a smaller turbine housing was just the final straw.

I think instead of dropping the turbine housing to a .85 to try and solve my lag issues, I will instead focus my efforts on optimizing my setup as best I can. Even with the relatively large turbine housing, I shouldn't have as much lag as I do, with the turbo being a dual ball bearing and all. So, I think I can help myself in other areas, like the WG spring, which I've already changed out.

Nick
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Old 07-19-17, 08:20 PM
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"Thermal conductivity is a material property describing the ability to conduct heat."

higher number =s more heat conductivity =s bad

Aluminum 205 (think LIM runners conducting heat into your charge air)

Steel 43

Stainless Steel 16

Titanium 22 (looks nice though)

Mica .71 (12 X 13 X 1/8th inch barrier about $65 McMaster Carr P/N 85165K81)

combine mica panel w a PTP Lava blanket and you are set.

picture tomorrow
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Old 07-19-17, 08:43 PM
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Originally Posted by Howard Coleman CPR View Post
"Thermal conductivity is a material property describing the ability to conduct heat."

higher number =s more heat conductivity =s bad

Aluminum 205 (think LIM runners conducting heat into your charge air)

Steel 43

Stainless Steel 16

Titanium 22 (looks nice though)

Mica .71 (12 X 13 X 1/8th inch barrier about $65 McMaster Carr P/N 85165K81)

combine mica panel w a PTP Lava blanket and you are set.

picture tomorrow
Howard, I found some flexible mica from McMaster Carr as I don't know if the 1/8th material will work with the limited space between my compressor housing and the LIM. We will see. I plan to get the LIM ceramic coated anyhow and see how much space I've got.

Nick
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Old 07-20-17, 08:03 AM
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'don't know from pic if this would help but...

the LIM has extraneous EGR passages cast into it and the only thing you need from the LIM is the runners. if you remove the LIM and have at it might you find clearance for the Mica barrier?
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Old 07-20-17, 10:38 AM
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On the subject of lag:

The size of the turbine housing determines how much exhaust energy it takes to generate boost (on low end) and is big determinant of backpressure on the high end, which affects power and knock.

Best way to think about it is this: If you floor it in 5th gear at say 3000rpm with the wastegate fully closed, the engine is very loaded down and all the exhaust is going to spin up the turbo. The size of the turbine housing has a big impact on how much boost you make there. It's less about how much time it takes to spin up the turbo, and more about how much energy it takes to do so. That's why the 2nd gen cars had a variable turbine A/R system and the 3rd gen cars had sequential turbos.

It takes less energy to get the turbo spinning with a smaller hotside, so if you are around town, going up hill in 5th gear you won't need to downshift so much.

Having a ball bearing turbo is what helps you in a transient situation, like going from off to on throttle as you shift, or if you are accelerating in a low gear and the engine isn't loaded down so much. If the turbine housing is too big to make the torque in a heavily loaded situation (5th gear WOT), the ball bearing isn't going to help.
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Old 07-20-17, 12:33 PM
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^^
Another factor that affects the "static" relationship of how much boost you can make per given rpm (what I call spool) is the compressor surge line on the compressor though.

On a turbo larger than about 57mm inducer on a rotary the surge line usually limits peak boost achievable per rpm no matter what you do with the hot side.

This has been driven home to us with the advent of the EFR turbos and their fast spooling Gamma-Ti exhaust wheels where when pushed the turbos hit the surge line so hard the car bucks.

A GT4088R is most definitely surge line limited on the typical rotary set-up in the low rpm (~0-4,000rpm).

Smaller exhaust side AR on GT4088R could help turbo transient operation (what I call response), but if the set-up is anywhere near optimal it should not affect the static relationship of peak boost per given rpm (spool).

Obviously, if you are asking a GT4088R to breath through a 2.5" exhaust with a cat a change from a 1.45AR to 0.85AR will positively affect spool as well as response.

I am talking about what we typically do with the rotary and turbos.
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Old 07-20-17, 01:35 PM
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Originally Posted by Howard Coleman CPR View Post
'don't know from pic if this would help but...

the LIM has extraneous EGR passages cast into it and the only thing you need from the LIM is the runners. if you remove the LIM and have at it might you find clearance for the Mica barrier?
Hence the reason I just purchased a JDM LIM which has much smaller passages. I will certainly be able to use mica to shield the turbine housing, but the compressor housing is so close that I doubt I could, on the forward-most runner of the LIM. The compressor housing obviously gets hot, but if the LIM is ceramic coated, perhaps it will be sufficient to mitigate the heat from the compressor housing on that one runner and I can shield the other three with the mica. That being said, perhaps by shielding with the mica, I'll create richer mixtures in the rear 3 runners and a leaner mixture in the forward most...?

Originally Posted by arghx View Post
On the subject of lag:

The size of the turbine housing determines how much exhaust energy it takes to generate boost (on low end) and is big determinant of backpressure on the high end, which affects power and knock.

Best way to think about it is this: If you floor it in 5th gear at say 3000rpm with the wastegate fully closed, the engine is very loaded down and all the exhaust is going to spin up the turbo. The size of the turbine housing has a big impact on how much boost you make there. It's less about how much time it takes to spin up the turbo, and more about how much energy it takes to do so. That's why the 2nd gen cars had a variable turbine A/R system and the 3rd gen cars had sequential turbos.

It takes less energy to get the turbo spinning with a smaller hotside, so if you are around town, going up hill in 5th gear you won't need to downshift so much.

Having a ball bearing turbo is what helps you in a transient situation, like going from off to on throttle as you shift, or if you are accelerating in a low gear and the engine isn't loaded down so much. If the turbine housing is too big to make the torque in a heavily loaded situation (5th gear WOT), the ball bearing isn't going to help.
I appreciate you taking the time to explain the ball bearing point. On the "streets" the ball bearing turbos were to give you quicker spool up. Though, it seems that isn't really the case now that you've explained it. Perhaps they allow you to better stay in the power when you're changing gears in racing situations and in a way help with reducing lag, but not from a WOT perspective from lower RPM range -- if I understood you correctly.

Originally Posted by BLUE TII View Post
^^
Another factor that affects the "static" relationship of how much boost you can make per given rpm (what I call spool) is the compressor surge line on the compressor though.

On a turbo larger than about 57mm inducer on a rotary the surge line usually limits peak boost achievable per rpm no matter what you do with the hot side.

This has been driven home to us with the advent of the EFR turbos and their fast spooling Gamma-Ti exhaust wheels where when pushed the turbos hit the surge line so hard the car bucks.

A GT4088R is most definitely surge line limited on the typical rotary set-up in the low rpm (~0-4,000rpm).

Smaller exhaust side AR on GT4088R could help turbo transient operation (what I call response), but if the set-up is anywhere near optimal it should not affect the static relationship of peak boost per given rpm (spool).

Obviously, if you are asking a GT4088R to breath through a 2.5" exhaust with a cat a change from a 1.45AR to 0.85AR will positively affect spool as well as response.

I am talking about what we typically do with the rotary and turbos.
If I understand you correct, you're basically saying that changing to the smaller A/R, so long as everything else is efficient enough, shouldn't make such a big difference from 0-4,000 RPMs...?

I do have a 3" downpipe of course, but the wastegate is recirculated. I've considered having a new downpipe made with a dump instead, or simply modifying my own. My power goals for the time being are 425-450 whp, so perhaps the recirculated wastegate isn't a major factor at those levels?

I know from seeing Howard's writeup on his own manifold that the flow of exhaust gases is certainly affected by the design of the piping and to that end, my WG re-enters my 3" exhaust downstream at nearly a 90* which definitely isn't ideal. Perhaps a slight modification to the angle at which they meet from WG dump to exhaust would be necessary but I just don't know.

Nick

NOTE: My exhaust is 3" from downpipe to rear muffler, no resonators or cats in between.

Last edited by Brilliant7-LFC; 07-20-17 at 01:54 PM.
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Old 07-20-17, 02:53 PM
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If I understand you correct, you're basically saying that changing to the smaller A/R, so long as everything else is efficient enough, shouldn't make such a big difference from 0-4,000 RPMs...?
Oh, it will make a difference in the turbo response which is what you feel but don't see on a dyno sheet.

It is similar to going from 8.5CR to 10:1CR on the rotary. Makes a big difference in driving feel, but only a ~2% difference on the dyno sheet.

Might make a difference in dyno sheet as well if you are not able to drive the compressor to anywhere near the surge line.

--------

Here you can see that increasing the turbo exhaust side AR can actually increase low rpm power since it will increase engine VE and so shift the engine operating range to the Right of the surge line on the turbo compressor chart.




https://www.rx7club.com/single-turbo...558kw-1114618/

The chart on the Left shows 9180 1.05AR dyno in Red and the 9180 1.45AR dyno in Blue at the same boost in a back to back test.

In the lower part of the chart you can see the boost trace where the 1.45AR out spooled the 1.05AR exhaust housing.

Chart on Right shows final 1.45AR numbers with higher boost in Blue compared to the same old 1.05AR numbers in Red.

Still, boost response is snappier with the smaller 1.05AR exhaust housing.
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Old 07-20-17, 03:28 PM
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Originally Posted by BLUE TII View Post
Oh, it will make a difference in the turbo response which is what you feel but don't see on a dyno sheet.

It is similar to going from 8.5CR to 10:1CR on the rotary. Makes a big difference in driving feel, but only a ~2% difference on the dyno sheet.

Might make a difference in dyno sheet as well if you are not able to drive the compressor to anywhere near the surge line.

--------

Here you can see that increasing the turbo exhaust side AR can actually increase low rpm power since it will increase engine VE and so shift the engine operating range to the Right of the surge line on the turbo compressor chart.

The chart on the Left shows 9180 1.05AR dyno in Red and the 9180 1.45AR dyno in Blue at the same boost in a back to back test.

In the lower part of the chart you can see the boost trace where the 1.45AR out spooled the 1.05AR exhaust housing.

Chart on Right shows final 1.45AR numbers with higher boost in Blue compared to the same old 1.05AR numbers in Red.

Still, boost response is snappier with the smaller 1.05AR exhaust housing.
Awesome data! Props to whoever did that back to back test because the difference is pretty clear. To me, I'd be a fool then to drop down to the .85 housing. No question that the smaller turbine housing would yield a more immediate feel to the throttle pedal, but it seems as though you're sacrificing power across the board. Not just in the top end, but in the mid-range as well.

In other news, I painted the "modified" strut tower support and will upload a couple pics tomorrow to show you fine gentlemen my skills with a hammer and can of VHT. I used the hi temp engine paint which I think should be fine. 550* is quite hot considering there will be a blanket on this bad boy soon...

I'm also running water lines to the turbo and am having a little difficulty clocking the CHRA, which is states you should do, to the tune of 20* to optimize the siphoning effect after shut down. With the blanket on, the temps inside the CHRA should be significantly higher after shut down and I'd like to utilize this integrated feature to lessen the fatigue on the bearings.

The bolts that go into the turbine housing appear to have been sort of chiseled so they don't back out and are locked down. I haven't tried turning them for fear of breaking them. Do you guys have any feedback for me on that? Should I just take it to a turbo shop and ask them to do it?

Thanks guys!

Nick
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