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Deciding on turbo for potential twinscroll build
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Old 10-18-19, 02:13 PM   #1
stealthlead
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Default Deciding on turbo for potential twinscroll build

Hey guys, I've been trying to plan out this build for quite some time and I feel like I have most of it figured out pretty well except the turbo. The goal is to have a really responsive street car that has great spool and is a blast to drive. It may be a car that transitions into a track car eventually so I'd rather overbuild it a bit versus under building it if possible; but for now, I'd rather keep the former in mind. Originally I was hoping to hit 600hp but after seeing some local cars and talking to a couple guys, I think 500 would be more than sufficient for the end goal if I had to put a number on it.

Car is a 04 STi that currently has a built motor with 100mm weisco's, bc rods, cosworth mains, a new nitrated STi crank and stock STi heads that have been refreshed. I know running 100mm's is risky, so the initial tune will be relatively conservative before stepping up to an IAG staged block (at least a 2.5) paired with stage 5 pnp'd heads. The tuner is well aware of the situation (he put the break in and daily tune on) and feels comfortable pushing it to 400 as long as it stays under 30 psi (it has been running strong for 15k miles @ 318hp/348tq on 22psi via a vf48 from a 15 STi). It will be ran well above sea level in Denver.

Intercooler core is an ETS 3.5". The twinscroll/rotated kit is being made by Evan @ BnM. Originally I was planning on an EFR build, but I settled on a TS GTX3576R. My tuner advised me it would be a waste of money for this altitude and is really pushing either a 3582r or G-series on me. I don't really have a problem with the G-series, in fact they seem to be doing really well. But every time I talk to someone that has an EFR they absolutely love them and swear by them, so I'm leaning more towards an EFR again.

The main deterrent for a twinscroll for me was space, particularly with twin EWG's that were going to be rerouted back into the DP (this is because I personally do not care for EWG's that vent to atmosphere). However from what I understand the EFR's can be internally gated successfully at high HP and also don't require a BOV as they recirc. This is a huge plus for me personally as I won't have to worry about the extra piping and dual waste gates quite as much.

What I'm asking for is advice from those of you who have been where I'm trying to go and your thoughts on the potential turbo selection, and overall build if you care to chime in. In addition if I was to go with an EFR series, I'm not sure if sticking to the 7163 or stepping up to the 7670 would be a better idea in my case. As mentioned, spool and response is a main concern but I don't want to also limit myself in the event I want to grow.

For clarification supporting mods have/will be done; braking and handling system reworked, rebuilt rear diff, hubs converted to 114 with new wheels, 255/265 tires, and the fuel system will likely comprise of a new in tank pump with 2 external pumps as well as a surge tank & new lines. Any advice or constructive criticism is appreciated.

Last edited by stealthlead; 10-18-19 at 02:20 PM.
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Old 10-18-19, 02:40 PM   #2
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Default Re: Deciding on turbo for potential twinscroll build

500-600 whp and responsive street car don't necessarily go well together. I only say this because I'm not sure what your past experience is with this platform or that power level. That is a lot of power for the street.. with that comes extra lag and illegal speeds come quickly.

To me, a 350-400 whp twin scroll setup on E85 would make for a fun & responsive street car. For others, they're never satisfied with any amount of horsepower.

I've heard great things about EFR turbos. The G series are just as good, but more expensive from what I've read.

My vote would probably be for a twin scroll EFR 7163 as a happy medium. My ideal setup would either be a Killer B ELH mated to the EFR 6758 or a JDM twin scroll manifold mated to the Blouch Dom 1.5 XT-R TS as a cheaper option.

You could always wait for the future of turbos, Garretts e-turbo
E-Turbo Technology - Garrett Motion

Hopefully yamahaSHO will chime in.

Last edited by STINick19; 10-18-19 at 03:19 PM.
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Old 10-18-19, 04:43 PM   #3
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Default Re: Deciding on turbo for potential twinscroll build

EFR 8374!

As already mentioned, the 7163 is a solid turbo for a street car. Leemanfor has a single scroll 7163 on a FMIC and at this altitude (also Denver), I think we can hit 30 PSI by 3,800 RPM. I'd have to go back and look at logs. I have to do some adjustment on his tune as he is hooking up the second port of his EWG. On the dyno, I could not hold 30 PSI. Even dropping boost, it made 461whp/461wtq on Edge's dyno (I've read it's 11-14% lower than a DynoJet).

I have an EFR 6758 that made 405whp/420wtq on Edge's dyno. If you want a ride, it has to be soon as it will be on The best vintage and classic cars for sale online | Bring a Trailer in about a week.

I'm sure Kevin would take you for a ride with the 7163.
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Old 10-18-19, 05:04 PM   #4
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Default Re: Deciding on turbo for potential twinscroll build

Thanks for the replies!

From what I understand 500-600 is pretty up there for street, which is why I'm reconsidering the turbo selection and dialing it down versus what was previously planned, so thanks for chiming in about that! Admittedly this is my first real car I've ever built, and I'm limited to what I've experienced with this car and what small time I've had in others cars. I have yet to ride in an car running an EFR. I also forgot to mention the car will be on E85 regardless of the selection. I also think I forgot to mention this is definitely not a DD - I have a camo 19' crosstrek limited for that


Quote:
Originally Posted by yamahaSHO View Post
EFR 8374!

As already mentioned, the 7163 is a solid turbo for a street car. Leemanfor has a single scroll 7163 on a FMIC and at this altitude (also Denver), I think we can hit 30 PSI by 3,800 RPM. I'd have to go back and look at logs. I have to do some adjustment on his tune as he is hooking up the second port of his EWG. On the dyno, I could not hold 30 PSI. Even dropping boost, it made 461whp/461wtq on Edge's dyno (I've read it's 11-14% lower than a DynoJet).

I have an EFR 6758 that made 405whp/420wtq on Edge's dyno. If you want a ride, it has to be soon as it will be on The best vintage and classic cars for sale online | Bring a Trailer in about a week.

I'm sure Kevin would take you for a ride with the 7163.

Thanks for the reply! I'm curious why you recommend an 8374, I'm definitely not opposed to going bigger though and plus that would mean I'd have an excuse to try out one of their new black series I think they're supposed to have even better spool and numbers. Those are still some pretty respectable numbers for that single scroll considering our altitude and the boost issue's. If possible, I would love to go for a ride in either one, I'll PM you!
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Old 10-18-19, 06:00 PM   #5
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I absolutely love my 7163. It's an amazing turbo for street driving, and super responsive.

I'm running a bnm single scroll setup with the indy car EWG housing.

The car will make 30 psi at 3800ish on the street and my build is basically an IAG stage 2 block that I built myself.

If you want, you can PM me any questions you may have. Depending on they dyno, you probably won't make more than 500 whp on this turbo without pushing it.

And if you want a ride, let me know.
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Old 10-19-19, 07:29 AM   #6
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Default Re: Deciding on turbo for potential twinscroll build

I have a full race twin scroll ewg manifold with a efr 7670 1.05 ar. The turbo is very responsive for what it is, I really don't think it has a lot of lag. An example would be when my car was tuned I reversed the boost controller lines accidentally as the tuner took power out of it the power was increased instead. At 3900 rpm's on 93 octane the turbo pushed to 35psi and made 490whp which is pretty responsive even the tuner was surprised on how quickly it spools up.

With that being said I do wonder how much of a difference in lag there is comparing my 7670 to a 8374 92 IWG any one have an experiences?
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Old 10-20-19, 06:58 AM   #7
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Default Re: Deciding on turbo for potential twinscroll build

Quote:
Originally Posted by nj kiter View Post
I have a full race twin scroll ewg manifold with a efr 7670 1.05 ar. The turbo is very responsive for what it is, I really don't think it has a lot of lag. An example would be when my car was tuned I reversed the boost controller lines accidentally as the tuner took power out of it the power was increased instead. At 3900 rpm's on 93 octane the turbo pushed to 35psi and made 490whp which is pretty responsive even the tuner was surprised on how quickly it spools up.

With that being said I do wonder how much of a difference in lag there is comparing my 7670 to a 8374 92 IWG any one have an experiences?

It sounds like its comparable to the 7163 spool wise, just a tad bit later. I'm curious about this as well, even more so about borg warners newer 'black' version EFR's which are only available in the 8374 and up. To me I'm pretty sold on the EFR's, at this point its just figuring out which size would best suit me. Do you ever get tired of the EWG's?
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Old 10-20-19, 08:23 AM   #8
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Default Re: Deciding on turbo for potential twinscroll build

The Black is 8474 and up. That starts at 95 lbs/min and only goes up.
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Old 10-20-19, 10:39 AM   #9
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Default Re: Deciding on turbo for potential twinscroll build

For an EJ25 I would stick to single scroll. All the SS vs TS testing we've ever done, the SS always makes more area under the curve AND more peak power. Both turbine technologies have their benefits, but IMO if you want the best power on an EJ then SS is the best way to do it. If we were talking about the newer FA20 engine I would be arguing the opposite. Which turbine technology makes best optimized power often comes down to the engine design (bore/stroke, heads, etc...) you are working with.

I'm more a fan of the Garrett turbos, and I'm really looking forward to what the new G-Series will be capable of. So far it looks like it will be 'the' turbo for the next few years until BW comes out with there next competitive product.
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Old Yesterday, 03:52 PM   #10
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Default Re: Deciding on turbo for potential twinscroll build

Quote:
Originally Posted by killerbmotorsport View Post
For an EJ25 I would stick to single scroll. All the SS vs TS testing we've ever done, the SS always makes more area under the curve AND more peak power. Both turbine technologies have their benefits, but IMO if you want the best power on an EJ then SS is the best way to do it. If we were talking about the newer FA20 engine I would be arguing the opposite. Which turbine technology makes best optimized power often comes down to the engine design (bore/stroke, heads, etc...) you are working with.

I'm more a fan of the Garrett turbos, and I'm really looking forward to what the new G-Series will be capable of. So far it looks like it will be 'the' turbo for the next few years until BW comes out with there next competitive product.

Thanks for the response! IAG seems to be saying the same thing to me. My tuner doesn't seem to big a fan of TS either. Do you care to elaborate a little bit about the findings? I'm just curious as to why this would be with an EJ. In the testing performed, was there much difference in spool?



I'm also curious about the comment about the garrett. In my case, would you be recommending a garrett over a precision if I was to go the SS route? I'm honestly not necessarily sold on either, I'm just having a really hard time making this decision. The only thing I'm 100% certain on is I don't want an EWG unless its rerouted back into the DP and with a TS setup this is not feasible or cost effective.
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