turbo for my REPU
05-25-12, 03:15 AM
#1
turbo for my REPU
I need a little turbo advice. The final frontier is turbo so I'm going turbo in my REPU. 
I'm getting a used S5 stock turbo from a friend but it doesn't fit the chassis due to narrow frame rails so now I'm looking at TO4B and TO4E etc. Lots of cheap ones on eBay...
What would you recommend? I'm just looking for cheap.
I need to fab up a manifold anyway so T3 or T4 flange, divided or undivided, adding a wastegate and 3" downpipe etc are all options.
57 trim? P trim? 1.00 A/R? Divided = more low end response?
I need low end torque because it's a truck, so fast spool at lowish boost is more important than big HP numbers at high boost. Might not run an intercooler due to space limitations/difficulty of installation etc. So 10psi or less.
Engine specs are old school 4 port R5 13B ported to 74 spec (50 degree closing just like any T2 or FD secondary ports, but all four on mine). Exhaust ports are currently GSL-SE spec but I could go in and port to T2 spec. Boost prepped Nikki or weber DCOE are two carb options.
Currently has S4 NA rotors. Have FD rotors available. Currently has full flow oil squirters in the "competition" R5 eccentric shaft - will probably swap to checkball style if I tear down to use FD rotors. Also gotta drill a bigger oil return hole in the front cover for a 5/8" hose anyway.
I mention the FD rotors because they are a low compression option if needed to make 220+ reliable HP and loads of torque. But I understand the S4 NA rotors might be the better choice in order to keep good low end while off boost. But then I need to be much more careful in tuning. And an intercooler would be more necessary. Or would it?
Just looking for 220HP to double the stock 110HP of these trucks. But if I can get more without lagging spool... and adding an intercooler... Well, if you guys recommend an int, I'll have to see about getting one and making it fit somewhere, but remember a blow through carb cools its intake charge so it's not like I really need one. Or do I?
Thanks!
I'm getting a used S5 stock turbo from a friend but it doesn't fit the chassis due to narrow frame rails so now I'm looking at TO4B and TO4E etc. Lots of cheap ones on eBay...
What would you recommend? I'm just looking for cheap.
I need to fab up a manifold anyway so T3 or T4 flange, divided or undivided, adding a wastegate and 3" downpipe etc are all options.
57 trim? P trim? 1.00 A/R? Divided = more low end response?
I need low end torque because it's a truck, so fast spool at lowish boost is more important than big HP numbers at high boost. Might not run an intercooler due to space limitations/difficulty of installation etc. So 10psi or less.
Engine specs are old school 4 port R5 13B ported to 74 spec (50 degree closing just like any T2 or FD secondary ports, but all four on mine). Exhaust ports are currently GSL-SE spec but I could go in and port to T2 spec. Boost prepped Nikki or weber DCOE are two carb options.
Currently has S4 NA rotors. Have FD rotors available. Currently has full flow oil squirters in the "competition" R5 eccentric shaft - will probably swap to checkball style if I tear down to use FD rotors. Also gotta drill a bigger oil return hole in the front cover for a 5/8" hose anyway.
I mention the FD rotors because they are a low compression option if needed to make 220+ reliable HP and loads of torque. But I understand the S4 NA rotors might be the better choice in order to keep good low end while off boost. But then I need to be much more careful in tuning. And an intercooler would be more necessary. Or would it?
Just looking for 220HP to double the stock 110HP of these trucks. But if I can get more without lagging spool... and adding an intercooler... Well, if you guys recommend an int, I'll have to see about getting one and making it fit somewhere, but remember a blow through carb cools its intake charge so it's not like I really need one. Or do I?
Thanks!
05-25-12, 02:27 PM
#2
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If you're trying to do this on a budget, you're not afraid to make your own manifold, and you only want 220hp I'd go with something small like a Holset HX35. It runs a T3 flange (kind of) and they come with large enough hotsides for a rotary to breath.
The DSM guys have been using them to make good power for some time and should spool really well on a rotary.
Yes, run a intercooler, especially if you're running those 9.4 compression rotors. You won't need anything crazy big if you're only looking to make 220hp
As long as your power goals are that low I'd keep the 9.4 rotors for the extra down low torque. Should also aid in spooling the turbo.
The DSM guys have been using them to make good power for some time and should spool really well on a rotary.
Yes, run a intercooler, especially if you're running those 9.4 compression rotors. You won't need anything crazy big if you're only looking to make 220hp
As long as your power goals are that low I'd keep the 9.4 rotors for the extra down low torque. Should also aid in spooling the turbo.
05-25-12, 08:58 PM
#3
Thanks for responding. 220HP is just my minimum goal now. If the turbo naturally wants to do more, cool!
Yeah I'll have to make my own manifold due to narrow frame rails. I may swap to the FD rotors, actually. I gotta get into the engine to deal with the shaft squirters anyway. Just a gasket set and some time at this point.
I built the engine for a supercharger originally. Well the SC is going elsewhere so the sky's the limit now. So I'm thinking FD rotors. And an intercooler.
Man, I know nothing about the HX turbos.
Got any numbers for the to4 series turbos? I think I'd like a T4 divided flange. I want fast spool, so a small A/R? Should I be at all interested in a T3/T4 hybrid? That's a T3 flange though, might be undivided. I hear they do like 300 on a rotary and spool fast like the stock HT18 though.
I wish I could use the S5 HT18 and the stock exhaust manifold. Then I wouldn't have started this thread.
Yeah, how about something that spools fast like the HT18 but in a T3 or T4 style turbo and can make 300HP easily? Only looking to run up to 15psi so I don't need to use race gas or aux injection. Is that a typical limit? Or is 18psi pushing it?
Yeah I'll have to make my own manifold due to narrow frame rails. I may swap to the FD rotors, actually. I gotta get into the engine to deal with the shaft squirters anyway. Just a gasket set and some time at this point.
I built the engine for a supercharger originally. Well the SC is going elsewhere so the sky's the limit now. So I'm thinking FD rotors.
And an intercooler.Man, I know nothing about the HX turbos.
Got any numbers for the to4 series turbos? I think I'd like a T4 divided flange. I want fast spool, so a small A/R? Should I be at all interested in a T3/T4 hybrid? That's a T3 flange though, might be undivided. I hear they do like 300 on a rotary and spool fast like the stock HT18 though.I wish I could use the S5 HT18 and the stock exhaust manifold. Then I wouldn't have started this thread.
Yeah, how about something that spools fast like the HT18 but in a T3 or T4 style turbo and can make 300HP easily? Only looking to run up to 15psi so I don't need to use race gas or aux injection. Is that a typical limit? Or is 18psi pushing it?
05-25-12, 09:44 PM
#5
Is yours a 77? I found they will fit in a 77 due to the slant in the frame where the waste gate actuators are. But mine is a 74 so no slant. Plus I dislike the stock twins with a passion.
I prefer blow through carbs to keep it simple. I hope the Nikki performs well.
I prefer blow through carbs to keep it simple. I hope the Nikki performs well.
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05-26-12, 08:29 PM
#8
No sorry. One bit of advice I will give you though no matter what turbo you get is make sure you have a lsd in the rear and get rid of the 4.62 gear.. Even with 17 inch tires and a lsd in the rear I would spin so bad through the first three gears it wasn't even fun until I got the 3.90s.
05-27-12, 12:18 AM
#9
Actually funny story about that. My friend's 77 had a 3.90 rear gear stock and 17 inch rims. When I'd follow him in my 74, our RPMs were exactly the same in the same gear and same speed! That means my truck is geared like a 77 with 390 gears and 17" rims. I could tell because his exhaust was so loud I could hear it inside my truck and it would "beat" with my engine's sound at the same volume.
My other REPU, the white one, does have a true 74 4.625. You can totally tell the difference. My red truck has always felt really tall geared, like someone swapped in a 77 diff at some point. It could never creep in 1st at a low speed because it always went too fast even at a somewhat low idle.
Also because of this tall gearing, it could never accelerate like you'd expect a 74 to do. I was never satisfied with the perceived lack of low end torque until recently when I added the Camden supercharger, long primary exhaust which enhances low end torque, and the 9.4 rotors.
In a way it would be counter-productive to pull this seemingly perfect setup to try an untested turbo setup. However I was wholey impressed by a blow through weber 45 DCOE on a streetported R5 13B and an S5 turbo in PercentSevenC's 83 GSL. This setup is available, or will be soon.
Before he added the turbe, his car had very little low end torque, as you'd expect from a big streetport and a big two barrel. Now with the turbo its low end torque is amazing. Its high end is also amazing. It just lacks a little in the driveability department - something I'd need in the truck. Plus its gas mileage is like 11 to the gallon. Of course my truck used to get only 10 per gallon back when it had a crappy exhaust, a stock carb and a dying tranny. I'm thinking the supercharger gets a lot better than that because it mixes the A/F so well, the carb can be tuned pretty badly and it will still work, even right out of the box, which it does.
So I don't know man. Part of my motivation was so the current long primary exhaust could come out and go in another REPU so I don't have to wallow around under the other REPU to create another one of these time consuming over-complicated exhaust systems. I figured a turbo exhaust system would go together a lot faster, then I could swap and I'm done.
Then again I've done these types of REPU long primary exhaust systems twice now. It might go a lot faster third time around?
But the way things are looking now, I'd be better off creating a new exhaust for the other REPU straight up and keeping this one on my red one and sticking with the Camden a little longer. Heck I haven't outgrown it yet plus the engine is a fresh rebuild.
Hey, if there was a way to guarantee the righteous V8-like low end torque of my current setup with a turbo and a blow through carb, I'd go for it.
My other REPU, the white one, does have a true 74 4.625. You can totally tell the difference. My red truck has always felt really tall geared, like someone swapped in a 77 diff at some point. It could never creep in 1st at a low speed because it always went too fast even at a somewhat low idle.
Also because of this tall gearing, it could never accelerate like you'd expect a 74 to do. I was never satisfied with the perceived lack of low end torque until recently when I added the Camden supercharger, long primary exhaust which enhances low end torque, and the 9.4 rotors.
In a way it would be counter-productive to pull this seemingly perfect setup to try an untested turbo setup. However I was wholey impressed by a blow through weber 45 DCOE on a streetported R5 13B and an S5 turbo in PercentSevenC's 83 GSL. This setup is available, or will be soon.
Before he added the turbe, his car had very little low end torque, as you'd expect from a big streetport and a big two barrel. Now with the turbo its low end torque is amazing. Its high end is also amazing. It just lacks a little in the driveability department - something I'd need in the truck. Plus its gas mileage is like 11 to the gallon. Of course my truck used to get only 10 per gallon back when it had a crappy exhaust, a stock carb and a dying tranny. I'm thinking the supercharger gets a lot better than that because it mixes the A/F so well, the carb can be tuned pretty badly and it will still work, even right out of the box, which it does.
So I don't know man. Part of my motivation was so the current long primary exhaust could come out and go in another REPU so I don't have to wallow around under the other REPU to create another one of these time consuming over-complicated exhaust systems. I figured a turbo exhaust system would go together a lot faster, then I could swap and I'm done.
Then again I've done these types of REPU long primary exhaust systems twice now. It might go a lot faster third time around?
But the way things are looking now, I'd be better off creating a new exhaust for the other REPU straight up and keeping this one on my red one and sticking with the Camden a little longer. Heck I haven't outgrown it yet plus the engine is a fresh rebuild.
Hey, if there was a way to guarantee the righteous V8-like low end torque of my current setup with a turbo and a blow through carb, I'd go for it.
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