I'd port the wastegate. It couldnt hurt. I crunched the numbers and you can get 10% bigger area shaving .5 mm off the openings, and most likely can take more offf than that. It might make all the difference.
Failing that run a small EWg in conjunction or just switch to full EWG hotside with proper twin gates or large single with a divided runner.

Here's me getting all HC on your asses; (actually just working it out here for my own benefit for lack of pen and paper)

area of 36mm wg;
pi18 squre=1,017.9
area of divider assuming 4mm
36x4 = 144
1018-144= 874

area of 38mm circle =1134
3x38mm divider -114
=1020

So that,correct me if i'm wrong, is about a 15% increase from taking 1mm off the ID and .5mm off both sides of the divider. And without having a turbo in front of me, I dare say more can be removed. Im not sure how the extra wastegate flow affects exhaust manifold pressure, i dare say for every small gain in WG flow you'd get a bigger gain in boost control if things were marginal to start with.

We have started remote tuning another pump gas 8374 with a large street port and it holds 12.5 psi off the medium actuator(full pulls).

Thanks Elliott!
Could you (or the owner) post details on the build/setup (exhaust, ignition, etc.)?

It just doesn't make sense that there's a 10+ psi swing in minimum boost between similar setups.

I spoke again with the Borg Warner engineer, who sent me a few drawings of the housing, and encouraged me to try "Matchbot", they're turbo/wastegate sizing instrument (which is too complicated for me).

One thing that stands out from the drawings sent is the shapes of the two wastegate passages—they don't look at all even to me, or straight. Virtually impossible to port except for removing the divider, which looks to get quite thick in some places further in. It does look like someplace where casting variance could make a lot of difference. He kept telling me to put a boroscope on the passages and look for irregualities—ESPECIALLY with one that won't go below 26psi.

He seems to thing going to a 9180 would actually help, due to the larger hotside, which is sort runs counter to experiences people have (i.e. I've not heard of any boost creep issue with the 7670). I'd hate to lose some spool up time, but the spool is pretty ridiculous with this turbo to start with.

What are the thoughts from the turbo experts on that?

That looks like a cross sectional drawing which will not necessarily display the widest section of each passage, but just a view of both at one specific depth. as if you cut it in half with a band saw.

He also sent me these—I've no idea what they mean.

Men this must be very frustrating. I was so gun ho of the 8374 setup, I dump my suppose to be my new setup s363 and start buying parts for this turbo like the mnaifold, after reading this post i am at a standby right now and not sure if i should hold out or continued buying the parts to finished my setup.

Sounds like BW is being pretty helpful did you ask if they would swap out a housing for you?

If you can remove the divider you can port it. If you dont trust yourself with a die grinder take it to someone who is good at porting.
Edit: or as above see if BW will swap you another housing.

Those are the boost levels you want to run (cannot see them in the shot) but he is showing you the calculated wastegate percentages and they should be under 40% for the boost level you want to run.

What is tough using that calculator is guestimating what the VE percentage is and what size engine to use for our rotaries.

He is showing you that you want to run an 80MM turbine wheel.

The A/R of the turbine is less important than the wheel size. I would go with a smaller A/R and a larger turbine wheel if you want spool and flow.

It is unfortunate that you cannot control the boost like you want with the 8374 IWG. It seems as though you are in the minority, with only a few people having issues controlling boost.

The rep is saying to run a larger turbine wheel because it flows more volume, and the engine flows a certain volume, hence less needs to be wastegated.

Interesting question I've been discussing with Brian @ Borg Warner.

I've not heard of anyone having trouble controlling boost with the 7670, but are there people having trouble? Based on the dynamic we've been discussing whereby the 9180 should be MORE controllable due to the 80mm exhaust wheel flowing more, the 7670 should have RAMPANT control issues with the 70mm wheel.

They are all the same exhaust housing casting, just with a different contour for the wheel.

Excellent observation. So you have the volume of the engine and how much volume of flow it can move. the secondary part is how much can the turbo flow through the volume of the engine and at what efficiency range right?

so perhaps the 8374 is much more efficient and is the sweet spot for this engine, hence it can flow a lot more volume and at a much cooler temp making a lot more power/flow, when you try dialing down a lot more flow you need more wastegate to hold say a 10PSI value.

With the 7670 you aren't flowing as much volume of air (compressor is smaller) and isn't in its sweet spot for efficiency, hence you don't need as much wastegate.

so you either "choke" the flow going into the engine, or your let it all flow out the wheel at the back of the engine (9180). Keep in mind that a 9180 isn't in its peak efficiency range till the upper rpms, not like the 8374 which basically travels up peak efficiency when ramping into boost.

it seems as though the efr 8374 doesn't choke it on the compressor side, but flows enough to not choke the engine on the turbine side needing a lot of wastegate which is just a hair too small leading to boost creep.

There might also be other factors with your engine that lead to worsening the issue. We do have a lot of people running these turbos at sea level who can maintain a pretty low boost pressure with these IWG.

Obviously I don't know the exact root cause but this is all speculation.

Let's look at what we could do to reduce PSI

Here might be some solutions.

1) increase wastegate size.
2) decrease flow into engine.
3) decrease velocity of flow into turbo.

Basically change the VE of the engine.

Run a small air filter, decrease exhaust piping after turbo, run larger manifold runners, whatever else people can think of. perhaps run a smaller intercooler with large pressure drop across it.

ptrhahn


Interesting question I've been discussing with Brian @ Borg Warner.

I've not heard of anyone having trouble controlling boost with the 7670, but are there people having trouble? Based on the dynamic we've been discussing whereby the 9180 should be MORE controllable due to the 80mm exhaust wheel flowing more, the 7670 should have RAMPANT control issues with the 70mm wheel.

They are all the same exhaust housing casting, just with a different contour for the wheel.

The 7670 has a couple factors working for it that help prevent boost creep on the rotary.

On the top end the little compressor just flat runs out of flow on a rotary. Most it can pump out is 18-22psi on a street port. If you crank the boost up above that for low end torque as I did it is dropping by 5,000rpm anyways.

Additionally the small exhaust wheel increases EMP killing the engine VE. Less power = less exhaust

-----

The 8374 has a larger compressor, so obviously can flow more air and therefore creep easier on the top end.

The larger exhaust wheel on a rotary just means less EMP and more engine VE for more power = more exhaust.

Does Brian understand we are operating the 8374 in surge on a rotary? Most engines struggle to spool a turbo that size.

^^^ Tuning4life has go it.

You are likely struggling with boost creep where others aren't because your 8374 engine system does not have some restrictions that others have. Could be anything from intake filter to exhaust tip.

Simply add that restriction in (I would choose a 1.5" exhaust tip for the track or a high flow cat for a street car)

or go with dual 44mm wastegates.

or put the stock twins back on as your restriction.

or do a hybrid systems of your IWG system with an external WG manifold you will still have a nice quiet street car when driving normally and when you really really get on it or are at the track the external WG will open for great top end VE at the low boost you want.




----

Like I said before, I struggled with this boost creep problem using a 60-1 compressor and "P" trim exhaust wheel in the stock S5 1.00AR exhaust housing with its dual internal wastegates. Well, it started with "O" trim exhaust wheel and then went to clipped "P" trim which didn't help boost creep much.

This turbo set-up is very much like the EFR IWG and Turblown cast manifold.

I ported the wastegates, open vented them with their own downpipe, removed the flapper and ported out the holes and used a 60mm external WG.

Everything I did to improve WG flow also improved overal engine VE so the boost creep persisted (though it shifted from a midrange boost spike to top end terminal creep).

Finally I ported the turbo housing scrolls twice their initial width (divergent turbo housing AR) and ported the manifold runners and turbo housing runners huge up to the now huge wastegate passages (larger than turbo passages) with flow favoring the wastegates.

Had a tiny bit of very top end boost creep after this which I solved with lowering the WG spring to below the boost I wanted to run so the WG fully opened at low boost and used a MBC to bring boost back up.

Finally fixed the boost creep, but ofc the turbo spooled lazier in the low rpm from the larger exhaust runners.

I should have just kept the exhaust restriction because then the turbo had low end punch it just impeded flow on the top end exhaust flow enough to stop boost creep.

"Fixing" the boost creep killed low end power and did very little for top end power (small gain from increased engine VE at same boost).

Hmm. This all seems a little counterintuitive.

OK, well, if you opened up your wastegate and it made the creep the same, worse, or shifted it higher in the rpm range, could it be that the gate is opening too soon? I'd certainly rather see a little spike in the mid range.

Two points:

1. Dan Chadwick runs this turbo on a longer-runner manifold, and uses the HIGH BOOST canister to run 12 psi (he says the lower ones drop off). Here's what he sent me:

"Hi Peter, sorry for the delay, don't get on facebook much anymore. The lowest we get with the high boost spring is 13psi, Rock steady with no creep. We tried the medium spring but boost would fall off at about 12 psi."

2. Jacob Cartmill noticed a phenomenon whereby the medium canister actually controlled boost up top better than the low. This was in part where the directive to run the medium canister came.

Do I somehow need to have the wastegate crack later to limit VE?

I'm also thinking that "a little" restriction elsewhere isn't going to do the trick. I've been down that road with the twins.

Peter,

Do you want to just send me your IWG housing and I will get the WG divider removed? I think this will solve your issue and I would like to make this option available to the 2% of people who have creep issues( assuming it fixes it). To be clear this will be free of charge excluding inbound freight to us and done via mill.

Hmm. This all seems a little counterintuitive.

OK, well, if you opened up your wastegate and it made the creep the same, worse, or shifted it higher in the rpm range, could it be that the gate is opening too soon? I'd certainly rather see a little spike in the mid range.

The creep did shift to higher and higher rpm.

It should be noted that by the time I "fixed" the boost creep the system VE was so high that later when I went to raise the boost and max out the turbo the 60-1 could only muster 18psi. 340rwhp on 10psi, 380rwhp on 14psi and 385rwhp on 18psi.

Before all the WG work it was boost creeping over 20psi by 3,000rpm.


Do I somehow need to have the wastegate crack later to limit VE?

You have something there. It could be the wastegate closing some in the higher rpms with the stiffer actuator spring that is lowering their engine VE and keeping it from boost creeping.

At one point I ran my 60-1 with no wastegate what so ever. I would boost in the low rpm, but then it couldn't maintain boost in the high rpm.

I also found the same thing on my 7670. In initial tuning the WG line fell off and boost shot up to ~30psi in the low rpm, but then boost plummeted just as rapidly.

Normal turbo behavior if you look way back into the early days of turbo charging with "free floating" wastegate-less systems. Turbo and cam sizing was critical.

If you wanted to test this theory you would wire your WG flapper partially open to see if it still had boost creep.

Midrange boost might be too high from my experience, so get on the gas from high rpm only.

It goes without saying testing like this should be done on race gas.

If I understand the dynamics correctly on the actuator, if the VE theory was correct, ADDING pre-load to the canister should do the trick—it would crack later, and open less far. I assumed all canisters opened to the same place, regardless of the spring pressure, with only pre-load affecting the end-distance, but maybe that's not the case?

The only data point I have was that going from 3.5 turns to zero turns on the medium canister seemed to lower the boost about 2 psi, and switching to the low boost canister on zero turns had no affect, but that wasn't a highly controlled test (different times/temperatures). I could crank on a few turns and see what happens, and or try the stiffer spring (high) canister.

ALSO: to be clear about what Blue TII posted about the 8374 operating "in surge"... are we talking about compressor surge or turbine surge (the latter I've never heard of). If it's turbine, at what rpm roughly would this begin to happen?

Elliot, that is a gracious offer—I'm not in possession of the car at the moment, it's at IRP having the clutch fixed. I'll give you a call on it.

No idea whether porting would fix the issue, but extrude honing may work if the passageways are too tight for die grinding.

http://www.rlengines.com/images/extrude/extrude.jpg

WG divider and T4 divider removed up to the WG. This has increased the surface area, and direction of flow considerably. Very curious to see how this works out for Peter.

Do anyone know how setup an electronic boost controller on this type of setup? Do u have to use the solenoid that came with the turbo or u can bypassed it?

Hey I am just catching up with this thread.

My main comment on the above quoted part of your thread is that the turbo engineers at the suppliers like the one you spoke to are used to dealing with engine dynos and turbo gas stands. I could go into detail about what those two attachments actually mean, but that's not going to do you any good. The calculations they make require a lot of information that you just cannot supply to them with actual measured data, just guessing and heuristics (rule of thumb). There are a lot of correction factors involved as well.

I've dealt with this in my day job. When we are evaluating which turbo to go with, we have to make a separate Excel spreadsheet for each supplier. The Excel file has a ton of calculations, and while many of them are common the calculations are still bit different for each supplier, as each uses a bit different correction factors and assumptions.

The turbine map he sent you and that app/calculator he is using is mostly useless for you--not because the principles aren't sound though. You just don't have a lab in your garage.

Actually i was hoping someone have a greddy profec b configuration setup and not using the bw black soleniod valve. The Mac valve looks confusing.

you just replace the BW solenoid with the greddy solenoid... there is nothing special about the BW unit.

http://www.greddy.com/upload/file/PRofec_Bspec2.pdf

Hey guys anyone with this kit is exprience exhaust leak by the downpipe v-band or manifold?

v-bands get warped when welding very easily. you can get gaskets for them. I've gotten a few to help with my v-band leaks. (I don't have the turblown downpipe)

Cometic 3 Inch Vband Gasket

You can put some grease and grit in the V-band and twiddle it back and forth to lap it in too if it isn't too far out.

Had luck with that on the 1st v-band I welded where I hadn't learned that if you weld it in one go without a heatsink it will warp.

I've also had some luck with RTV copper... but I wouldn't try that on the turbo v-band. I used it on the v-band further down my exhaust.

There is a special efr v-band flange required for proper fitment. I don't know if it comes with the kit or not, but i made do with a regular male v-band flange that i massaged with a die grinder. The leaking was fairly minimal, and pretty much self sealed itself with carbon after running a few tanks of fuel.

This looks like a good thing. If I had known about these I would have grabbed a couple.

That gasket is legit :bubrub:

I can't count the number of single turbo FDs I've been around with leaky connections at the DP to turbine discharge.....

Would that gasket be able to take the heat? I wish there was a thin multi-layer copper gasket for vbands.

I just finished switching over to iwg. My car has large streetport, 3.5inch dp, 3.5 inch mp and a FEED ti catback which is slightly bigger than 3inch.

With that said, im holding 16psi with a 2.75inch restrictor plate in between my mp/catback.

This is with basically no preload and a turbosmart eboost street boost controller.

With 3 turns preload, no boost controller and no restrictor plate I was creeping to about 18psi after 6k rpm.

^Fancy that, the restrictor plate did indeed make a difference ;)

ArmenMAxx Would that gasket be able to take the heat? I wish there was a thin multi-layer copper gasket for vbands.


100% definitely not.
But it is super easy to use hole saws or tin snips to cut out many thin stainless sheets into multi-layer stainless (MLS) gaskets that DO survive.

I just finished switching over to iwg. My car has large streetport, 3.5inch dp, 3.5 inch mp and a FEED ti catback which is slightly bigger than 3inch.

With that said, im holding 16psi with a 2.75inch restrictor plate in between my mp/catback.


Yeah, it sucks to have to run a reducer (check that thing frequently, they bow out away from exhaust flow over time).

BUT I found running a 3.5" DP and Midpipe to a 3" cat back to limit boost (on an EWG system) gave better spool than just running 3" turbo back that didn't boost creep.

Did you find the same thing?

I definitely remember FEELING my setup having better response when switching from 3inch to 3.5inch. Especially transient response however in 4th gear high load it would hit 10psi at about the same rpm. Same can be said about switching my 8374 from ewg to iwg. It feels more response but I hit 10psi within 100rpm in high load.

I should note that right now I am hitting 16psi and holding it to redline without any creep. Its possible that I may be able to lower the boost more with my boost controller. It doesnt make sense, but I am able to hold lower boost with the boost controller vs no controller and no preload. Perhaps the controller is pushing door open further somehow? Again, doesnt make sense to me. Without the controller I would hold 14.5 psi and start to creep after 6k rpm. This was with the restrictor plate. I never wired the door open (lazy) to see how low my setup can hold boost mechanically. Either way, my afr's are at 10.0 and it still feels f*cking awesome as is. Sounds higher pitched vs my re-routed long runner ewg setup also.

I definitely remember FEELING my setup having better response when switching from 3inch to 3.5inch. Especially transient response however in 4th gear high load it would hit 10psi at about the same rpm.


Ah yes, that boost response is what I meant when I said better spool.

Peak boost by rpm with EFR 8374 is going to be dictated by the compressor map surge line.

Can't fix that with more exhaust energy from larger exhaust or tighter AR. You could fix it with bigger ports or another rotor.

it still feels f*cking awesome as is. Sounds higher pitched vs my re-routed long runner ewg setup also

Sweet! Put more vids up on Youtube if you haven't already. I enjoy watching those!

It doesnt make sense, but I am able to hold lower boost with the boost controller vs no controller and no preload. Perhaps the controller is pushing door open further somehow? Again, doesnt make sense to me. Without the controller I would hold 14.5 psi and start to creep after 6k rpm.

It is possible that your boost controller settings are CLOSING the wastegate some at high rpm which increase exhaust manifold pressure and chokes the engine VE in the high rpms so limiting boost creep.

As I described above to ptrhahn.

Dont want to clutter this thread. I did make a short canyon vid to showcase how responsive the IWG is and posted in my track vid thread.

https://www.rx7club.com/racing-kills.../#post12040441

I finally got around to examining my 8374 turbine housing. I'm the guy that has seen creep as high as 26 psi. The casting looked ok but there was definitely some room for improvement. I spent about 4 hours porting it today. I opened up the runners all the way to the gate. I tried to shape the runner entrances shear the gasses more efficiently. Unfortunately I won't be able to report the results for some time. I still have to finish assembling the motor and break it in before going boost crazy.

Nice work on the runners :icon_tup:

We just had another EFR IWG FD( REW SWAP ) hold 11psi on the dyno and street... OEM medium BW actuator with 3" full exhaust.

Keep in mind that Armen has a 3.5" DP/MP and 3.25" catback so its expected that he will be at much high boost pressures for a 42mm single WG.

I also finshed my setup and tested it yesterday in wot it hold boost at 11lbs max. my setup is 8374 with Bw actuator, Turbosource cast mani & downpipe, SMB hi flow cat with racing beat dual tip. I have to say you guys were right this setup it built boost very fast at partial throttle.

^with the HFC and restrictive RB dual tip CB, I wouldn't expect any kind of boost creep issues :)

Update: Well, I finally got around to pulling the car apart again to install the new housing, and it didn't go well.

First, somehow the tension nut on the actuator shaft was frozen on, and even after PB blaster and using a vice grip to hold the shaft from turning, it snapped the shaft off. I'd say it was impossible to have cross threaded, since it was 1/2" up the shaft where it sat.

The big problem, however, is I can't get the turbine housing off. It's been soaked to death in PB Blaster, and I tried both beating on the actuator bracket with a mallet to try to get it to rotate a little, and actually bolting the whole mess back in the car so I could get some leverage on it. Nothing. Like it's welded together.

A couple other observations:

1. With the T4 divider removed, it's really going to need an undivided gasket. That center piece is just going to flap in the breeze and just break off and go into the turbo. If I cut it off, it'll expose the material sealed inside.

2. The studs for the manifold are a hair too short. I used the crimped copper clad nuts, since the flangeless hardware store type nuts it came with would have no way to stay tight—there's no room for a nordlock or other washer, and the copper clad nuts are not that tall but really needed a couple more threads to get through the crimp. They came off REALLY easily. I don't know if it was leaking, but it would have if I did more than cruise it around the street.

3. Maybe I'm just in a bad mood now, but I am skeptical that this will actually work. When you look at the flow paths for the two divide wastegate runners, they are pretty good. I think the hole at the end is just not big enough, but I guess we'll see eventually.


In any case, I'm pretty much at a standstill. I might as well ship the turbo back and see if turbosource has any way to get it apart.

Also, can somebody tell me why every picture I post to the forum is upside down?!

I had a similar situation happen to me with the stuck housing. Literally had to tighten it back down in the engine bay and use a crowbar to wedge it off after using a blowtorch to heat it up. Sounds brutal but like you said, mallet, rotational forces, plus a can of pb blaster didnt do much.

Best of luck

According to this graph, you're WAY off above 4200-4300 RPM to Redline (according to factory tire size and final drive ratio).

The bumpiness of that curve suggests the engine would prefer a leaner AFR. Hey, my Integra loves 13.2-13.4 AFR on CA's 91 Octane, and MOST tuners would suggest 12.5ish for that car. Just saying...Dave should have known better by looking at that and tracing what the engine is asking for.

Timing could also be too conservative in this region...

Mmm. Not really. Mid 11's is where these cars ought to be... most rx7 tuners will tell you to BACK OFF if you start to see 12's at WOT.

It's more than likely tires slipping on the dyno—the same happened when Ray and I dyno's it.

Anyone try a single external gate setup?