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What turbo for road racing?

8K views 46 replies 16 participants last post by  Donnie 
#1 ·
What turbo are you guys running? I'm planning on getting my car set up for some Road Races nothing professional just for fun. I have an agp 50trim that makes 20psi around 3900-4k. There is a lot of lag to the turbo and I'm thinking I need something that will spool quicker to pull me out of the turns. The boost comes on hard at 3500 its makes 10psi then slams to 20 by 3900 and usually spins and torque steers, It pulls hard from that point to redline but when I shift it takes a second or 2 to build boost again. What are your subjection?

Thanks
 
#2 ·
Sounds like a boost leak, You should be seeing alot more boost by 3500 RPM
 
#3 ·
My stage 3 is just like stock boost but instead of 15 psi its 21. And ii like the power haven't tested around corners yet. Only been straight shots. Or you could look in to something like a persision I know they make a 50 trim like that spools up faster
 
#6 ·
I was thinking about the 5431 and I have been reading through the Precision turbo owners thread. I would like to keep the power levels around 380-400wph on 93 and I don't know if it will support that with pump gas. I was also thinking about the GTX3071r as well.

I don't believe that there is a boost leek as the spool of the turbo has been the same since I installed it. According to AGP this 50trim will max out around 480whp so that's where the slower spool comes from.
 
#9 ·
I just don't want to wait for the spool in a road race. On a drag strip it wouldn't be a problem wind it out and shift but if I'm down low in the rpms I would like some bottom power to pull me out of turns with out downshifting to 2nd spinning.
 
#10 ·
You can address this via better boost management. You mentioned in your 1st post that you have you boost set at 20 PSI? This leads me to believe you are using some sort of manual boost controller?

Wouldn't it be great to set your target boost for the gear you are in? You will make 10 or 12 PSI faster than you will make 20 PSI? See where I'm going?

Regardless of what turbo you end up getting, I think you will benefit from better boost control. Just my .02 cents.
 
#12 ·
You can address this via better boost management. You mentioned in your 1st post that you have you boost set at 20 PSI? This leads me to believe you are using some sort of manual boost controller?

Wouldn't it be great to set your target boost for the gear you are in? You will make 10 or 12 PSI faster than you will make 20 PSI? See where I'm going?

Regardless of what turbo you end up getting, I think you will benefit from better boost control. Just my .02 cents.

I agree with you I am using a mbc boost by gear is the way to go on any setup and a boost box is something I have been planing on getting for some time now. I just think a turbo with faster spool will work better on a road course.
 
#13 ·
If I had to guess with my setup I'm making in the high 300's and with a turbo that makes 20psi at almost 4k and is good for almost 500whp I would like to have a turbo with fast spool and make around 400whp. This turbo pulls like crazy after 4k I would like to move the power band down 500rpms
 
#15 ·
What manifold and a/r housing do you have? If you run a crappy log manifold and anything larger than a .63 and you are hurting your spool...
 
#28 ·
What manifold and a/r housing do you have? If you run a crappy log manifold and anything larger than a .63 and you are hurting your spool...
1lap! Do you mean a crappy manifold in design (vs. tubular)? Or crappy manifold in terms of quality (poor build construction)?
Also, what a/r do you u run?
 
#16 ·
Boost box and never look back this thing is amazing!
 
#20 ·
You should still be hitting more then 10Psi @3500
 
#26 ·
Thats sweet I bet it pulls hard does it pull all the way to redline?
Not quite... Only pulls to 7,400, then it falls off about 10%. :rofl:

Redline is 7,750
 
#29 ·
Stock is where it's at. :paranoid:

If I were building a car for road racing a Mopar Stage 3 or upgraded Stage 3 would be my likely choice although the new Borg-Warner EFR are mighty tempting for the power and spool characteristics. Lots of great turbos on the market today that weren't available just a few years back.
 
#32 ·
Stock is where it's at. :paranoid:

If I were building a car for road racing, a Mopar Stage 3 or upgraded Stage 3 would be my likely choice although the new Borg-Warner EFR are mighty tempting for the power and spool characteristics. Lots of great turbos on the market today that weren't available just a few years back.
Concur,

If I were building a road race car from scratch, a big wheel S3 would be my
1st choice.

I guess what I was trying to suggest to the OP was to try and optimize his current set up. Regardless of what turbo he's running, I think he could benefit from better boost management.

I'll admit I'm completely out of my element when it comes to road racing, but I would think a MBC would not be optimum.
 
#36 ·
Road racing and autocrossing are very different but I very rarely see below 3900rpm while autocrossing. During the few track days Ive done in my srt-4 I dont think I was much below that at any point. My car is way low on power compared to anyone else discussing this (300ish hp)

The only way you'll need to know if you need to adjust the car is to run it and see what happens.
 
#38 ·
Depends how much grip you have on the course. Auto cross != road racing. More grip, you can run slightly bigger turbos. I wouldn't go any bigger than a GT35 or equivalent. If you had the grip and downforce, a 42 could work. Then you need good engine management with a proper tune. Do it right and get a standalone.
 
#39 ·
"By design most log manifolds are going to fall into the crappy category... The work, but not nearly as well as a well built tubular...

I run a vband .63 TiAL housing. The vband also helps smooth the air flow to the turbo and improves the spool."

I don't mean to be mister smarty pants and may be misunderstanding you, however log and tubular aren't mutually exclusive traits in a turbo manifold.
SS Tubular Log Style Manifold for a Nissan KA24DE
https://lh3.googleusercontent.com/-uL-BF1rbobM/UMDAzAwW2FI/AAAAAAAAAA4/S0sYLcOg-
WQ/s640/SS+tube+log+mani+SR20.jpg
Carbon Steel Tubular Log manifold for a Honda D16Z6
https://lh6.googleusercontent.com/-...AAAAA8/oyaqqEexugc/s300/tube+log+mani+D16.jpg
Equal Length Runner Cast Manifold By HKS for the Mazda 13B-REW
https://lh6.googleusercontent.com/-...450/hks+CAST+EQ+LENGTH+RUNNER+FD+RX7+MANI.jpg
Equal Length Runner Cast Manifold By APR Tuning for the DOHC I4 VW
https://lh3.googleusercontent.com/-...q-CiTc/s226/CAST+EQ+LENGTH+RUNNER+VW+MANI.jpg
I do agree that log manifolds have by design kind of suck due to the fact that
unequal length runners will have unequal back pressure. Also, the log design tends negate the ability to do a true divided manifold, which in turn allows the
the splitting of the exhuast pulses between the two sides of a twin scroll turbo. An important feature on small cid even number cylinder/rotor motors. Faster spool being the most satisfying benefit of this.
Conversely, cast manifolds tend to outlast tubular manifolds (when well made) on account of there being no additional stress points for pressure and rapid heating/cooling to cuase fractures. Also, the manifold thickness isn't limited to what diameter pipe your shop/fabricator can get a hold of. Then, there's the matter properly welding thick pipe into a compact and complex shape.
Now, of course we could talk materials, but that's all blah, blah, blah.
 
#41 ·
Probably not. Casting a quality manifold is a huge investment for a company. It
was more of a technical statement than anything. Personally, if I were to go crazy with my skittle I'd go with a SS tubular manifold, fully divided between the paired cylinders with each half having its own external waste routing and waste gate. Ceramic coated to oblivion, completely nylon AN lined (including vac/boost) with DEI fire sleeve protecting them, and mated with a carefully chosen turbo for my specific application. However, if "ifs and "buts" were candies and nuts we'd all have a merry Christmas wouldn't we?
 
#47 ·
Fair enough. lol.

Try getting a damn near full knee surgery. If it weren't for my computer, I'm pretty sure I would have gone and sampled the flavor of my 12 Gauge's business end by now from sheer boredom. :rofl:
 
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