Best Turbo For Autocross

[Hijacker]

I got to thinking about this. I've been researching turbo upgrade options for the car recently, but i've been focusing on maximum horsepower instead of overall performance.

This past autocross was a killer in the tight turns as I would have to lay off the gas for a good amount while I slowed the car to get through the turn. The main killer was a near 180 keyhole turn that required the engine to downshift into 1st, or else the lag would be unbearable (one run I left it in second to see what would happen, and the lag cost me dearly).

As I get more into autocrossing, I realize I need a turbo that can spool up faster than the T25, so I've turned my search towards ball bearing turbos. I would love to have a GT25R, but there's a nagging in my head that says it's too much power for an autocross course and I'll never hit full boost with it.

For my goals (which is more road course than drag), what would be the best turbo to pair up to my engine? Any and all opinions welcome (as long as they're productive and non-flamitory). And before anybody screams "search", guess what. I already did

[VitaminT]

Maybe this will help. Please forgive me for linking to another board.

http://forums.freshalloy.com/u...&vc=1

the S-15 turbo car is a car i tuned. RWD s13 SR 299 HP @ 16 psi, stock block, stock cams, stock headgasket. OBX style manifold, Stock Cat, stock intake manifold.

for a Disco we can use the SCC project silvia. until someone else can post dyno graphs of this turbo on a SR.

lastly, for the GT25R another car i tuned. GT25R .86 A/R, hks 264 step 1 cams, stock intake manifold.

TQ at 3500 RPM

S-15 Ball bearing T-28 - 240 ft-lbsDisco Potato - 185 ft-lbsGT25R w/ .86 A/R - 165 ft-lbs

TQ at 4000 RPM

S15 turbo - 280 ft-lbsDisco Potato - 255 ft-lbsGT25R .86 A/R - 235 ft-lbs

Ok so the DP has the GT25R by a bit on spool, but lets look at top end performance.

s15 turbo 299 HP @ 6000Disco 278 HP @ 6100GT25R 360 HP @ 6500

Now heres how i interpret the data. the s-15 turbo KILLS both the other contenders in spool 55 ft-lbs tq gain over the DP at 3500 RPM. now THAT is what i consider to be a good performing responsive turbo. but hte catch 22 is that the s-15 turbo made more top end power as well??

so compare the gt25 and the DP and you'll see the DP does have the GT25R beat by a bit in spool time, but the GT25R gets 78 more HP on the top end.

I would say go with the S15 as it seems to spool like sometime yesterday. I am also sure other people can post as to the transient response/spool of the S15 turbo.

[Hijacker]

I finally read through the most of that thread, and an ajoining thread posted by Scott of SS. The GT series doesn't seem at all what I'm wanting anymore, but at the same time, I don't think I wanna drop a big T3/T04 combo in either.

The S15 might be my best bet for response vs power.

any other contendors in this mighty match for the best turbo?

[ItzGenX]

Try an antilag system of some sort to respool before you come out the turn. You need to double clutch during down shifts (and heal toe) and only rev with the clutch pedal up, hook up a switch for when it is down, floor it, insta-spool at set boost and a few flames at the apex of the turn, let off clutch and ease off gas a little and floor it again, you should be fully boosted right at the exit of the turn. It will probably take some getting used to. That is my only idea as to get some better spool out of these long hairpin turns. As for turbo choice, the T25 is one of the quickest spooling turbos besides one of those TINY turbos that won't make enough power during straights and long sweepers.

[Hijacker]

heel toe for me has always been a problem (my feet have always stuck out like a penguins), so my heel barely catches the gas pedal's corner. I'm sure if I got a new gas pedal, I'd have an easier time at it. I usually rev match when I'm expecting to down shift so as not to unsettle the car.

Autocross technique was not the point of this thread. I'm mulling over turbo options and want to hear people's opinions on a good turbo for road courses.

Also, setting up your prespool system would be costly and sounds suspiciously like a mis-firing system. The T25 is a decent turbo, but it has too many limitations for my tastes. Mainly in the lag vs total power aspects.

[Nismo_Freak]

FP Big28 or S15 Turbo

Both good.

[S13240]

Also, setting up your prespool system would be costly and sounds suspiciously like a mis-firing system. The T25 is a decent turbo, but it has too many limitations for my tastes. Mainly in the lag vs total power aspects.

It is a misfiring system. I say go for the FP t28 or s15 t28 as well.

[VitaminT]

HKS GT-RS?

[SeVa-S13]

I'm hurt that Bart gave me no credit for helping to spur on this idea. :pface Ever find out about that T28 I linked? Might not be a bad choice afterall.

[Hijacker]

the GT-R turbo is looking good now. I don't have the money to plunk down right now though so i can't bid on it. Plus a turbo is a big thing to get, so I want all my options thought thuroughly before I drop change on the part.

btw, thanks for sparking these thoughts in my head, Blake

[VitaminT]

If by GT-R you mean Skyline GT-R then just keep in mine that i believe the A/R's are different from the S14 and S15 T28. Good or bad I don't know.

[Dori Dori]

It's smaller...chances are you're peak output would be higher w/ a stock t25. It will spool faster though.

You could also look into the gt28rs...el disco potato. Everyone talks s*** about the scc car, but look at the nubers on atp's 1.8ltr Audi (w/ a stock exhaust too).

[Hijacker]

I've been reading a lot on the DP, and from the looks of it, it won't hit full spool till the early to mid 4000's. That's too late IMO for an autocross setup. I need something that is almost spooled up in the early 3k's. The stock T-25 so far has been good about spool up, but I've already got it pushing it's compressor limits and I need to have a bit more power for exiting turns. But do you have a link to any on ATP's audi? I would like to see what they think of the turbo on their car.

[DriftS14]

I have a vid that will show you how fast my Power Enterprise 1820 will spool. The boost is set to a lowly 8 PSI. I have a boost controller coming in the mail and I will take another vid at ~14 PSI. It spools just as fast as the T25 and is ~350-380 HP capable.

5 PSI is on tap at 3000 RPM with all 8 at 3500.

[Hijacker]

do you have the specs for the PE1820? Also, I know Phase2 sells them, but I can't imagine shelling out 2100 bucks for it.

[DriftS14]

I saw it for 1800 somewhere else, but I can't remember where. The spec are available on the power enterprise website.

[Hijacker]

1800 is still a lot for a turbo.

[VitaminT]

Yeah for real. HKS turbos are almost the same as some of the Garretts at twice the price. I guess they have that JDM tyte surcharge.

[Altiman94]

while autocrossing, my engine never gets below 4k revs. If you are a good enough driver you would never be experiencing boost lag.

[S13240]

I have a vid that will show you how fast my Power Enterprise 1820 will spool. The boost is set to a lowly 8 PSI. I have a boost controller coming in the mail and I will take another vid at ~14 PSI. It spools just as fast as the T25 and is ~350-380 HP capable.

5 PSI is on tap at 3000 RPM with all 8 at 3500.

Every site I've been to says it's rated around 320 only dude.

[DriftS14]

Every site I've been to says it's rated around 320 only dude.

Every site that I've been to says what I quoted. If your search for this turbo on google, you will see numerous WRX applications rating this turbo at 400 plus. Of course, to give you the benefit of the doubt, it may be to the flywheel. Rest assured though, 320 hp is not it's max.

[Dugi]

If you have the $$$ HKS GT-RS. pulls very strong thru the whole RPM range. very fast spool up. But a S15 T28 will also do. cheap and good

[Hijacker]

I'm starting to lean heavily towards the S15 T28. but income is needed, and I need to finish suspension and drivetrain first.

[Dori Dori]

http://www.atpturbo.com/root/r...o.gif

Remember, it's on a stock exhaust and the motor is a 1.8 so shift the graph up and over and you should get a general idea of what this turbo can do.

[VitaminT]

Made good power, but dang did it need a set of cams.

[S13240]

Every site that I've been to says what I quoted. If your search for this turbo on google, you will see numerous WRX applications rating this turbo at 400 plus. Of course, to give you the benefit of the doubt, it may be to the flywheel. Rest assured though, 320 hp is not it's max.

My mistake, I was thinking of the PE1420 LoL

[Dori Dori]

DriftS14, WRX's generally make somewhere in the low 300's whp with the PE1820. You can estimate that to whatever you want (being that they are awd), but any logical estimate won't yield 400+hp. I also find it odd that you say the pe1820 has good spool up characteristics meanwhile it's know in the WRX community as being a very laggy turbo, 'drag only', and said to not make full boost until after 4000rpm.

[DriftS14]

I agree with you. Everything I have read says that the 1820 is a "drag only" turbo too. The difference is that I have videos to prove the spool up time. I'm willing to bet you saw one of them (though not very good) on the boost creep topic. Now I could see it if there was a difference in opinion on what "quick spooling" really is. Perhaps that is where I am mistaken. In order for any tubo to make 20 PSI is going to take time. My 1820 offers me 8 PSI ("full boost") at 3500 rpm. I wouldn't doubt for a second that 20 PSI would come on at 4000. Question is, what does "full boost" mean to you?

[DriftS14]

Also the GT28RS' flow is rated at 35 lbs/min. The 1820 is 40 lbs/min. I don't know if 40 lbs/min will yield me 350, but I'm gonna try my best.

[compression]

I am running an S15 turbo on my S13, it spools pretty quick. Here are the specs on the trubo from the S15 silvia:Compressor side: 60 trim T-3 BCI-8 wheel in a.60 a/r TO4B housingExhaust side: 62 trim T25 turbine in a .64 a/r housing I dont have dyno number or any other useful info because i just go it running, i know it does hit 12psi pretty quick!

But for autocross, especially tight courses, honestly, turbo is not the way to go. All turbos have to spool, no matter how small. You never really get a chance to get up into the boost where the engine makes its real power. You need the immediate power of a n/a motor. Thats pretty much the truth. You dont see too many turbo cars at an autocross (well, except the wrx). You also dont have time in autocross to do the "slap the gas to keep the revs up" heel action that you see in road racing when on the brakes around a turn.

But maybe you can make it work and be successful, that would be great, I know it would take a lot of pracice....