toddk911

Can some Vitesse guys post about when you get full boost on high boost runs/dyno? I am just curious for comparison as Vitesse is at the forefront for turbos/spool up.

I see some Neon SRT guys getting 20+ psi by 3,300-3,600 but still have plenty of top end; turbo is not running out of steam AND spools pretty good.

I know Porschiphile will post, or should, as he knows a lot about more of the import markets.

http://www.orlandoforums.com/forum/s...=59878&page=11

schadenfreude

I have a VR stage 3 and get 1 bar at about 3200-3400 by the tacho in 4th (hard to tell exactly since the boost is rising so fast at this point).

However, I seem to have weak ignition as my car stumbles and chokes if I go WOT at 2000 rpm in 4th. Also I'm pretty sure I have cracked headers or some other exhaust leak as my spool has always been pretty lame. With a tial 38mm wastegate shut all the way via EBC spooling a 26/6, I'd only get 1 bar at ~3000 rpm in 4th which seems to be worse than what a lot of others get with the same config.

TRP951

They also do have their turbo right on the manifold so that helps quite a bit

toddk911

So their turbo is right off the exhaust manifold?

TRP951

yeah like a eclipse/talon/evo ect. but the manifold is at the back of the motor and the intake is on the front

Fishey

Stock SRT-4's the turbo is part of the manifold.. (IE doesn't unbolt)

Also, We have made mid 400whp out of our SRT-4 and it gets full boost by 3500RPM. (24psi)

Porschefile

That's right I'll post! To achieve ~20psi between ~3.3-3.6k rpm, most of them are probably not using any exhaust housing larger than a Garrett T3 .63 a/r. A twin scroll .78a/r would work though. This is assuming a Gt3071r, equivalent or larger turbo. Actually honestly most of the dynos I've ever seen for Srt4's among other small displacement forced induction cars generally tend to show power/tq dropping off up top most of the time with a .63a/r or smaller exhaust housing. Srt4's are no exception. They might hold power a bit better, but almost all of the dynos I've ever seen with exhaust housings that small usually show power/tq dropping off before 6k rpm. If they maintain or still make any power on the top-end where ours wouldn't, it's likely a result of the more efficient heads.

toddk911

Hey Bud!

Yea, it seems they are running smaller a/r in the .50 or so range.

But yet they are still running up to 25 psi???

RKD in OKC

Guy at work as an SRT. He is planning putting a 77 turbo on it. Shop is telling him to put two turbos in line to get quick spool and big power.

toddk911

Many say that is not the way to go, but I think it is. A lot of the big power Supra guys go from twin to single and they say it is better, but I don't know.

Example:

Like for us, a k26/6 inline with a k29/8 or 10. Then you have a ful tq curve from about 2,500-redline.

Porschefile

Twins are generally more "progressive" as boost comes on. Lots of people go single in that community because it is easier, less stuff in the engine bay, and once you get those big turbos spinning a bit (say like 7-10psi) the boost response goes nearly vertical. That's a large part of the reason you'll see those insane dynos where they gain like 700+whp within a 1-1.5k rpm range. In short, big singles generally tend to "hit" a lot harder, which is more fun to me. Technically twins are going to be a bit more responsive and offer a slightly wider powerband, but there are so many exceptions that it's not always true. Twin turbo setups are a waste of time on a 4 cylinder IMO. All you'd achieve is increased weight, complexity, and maybe a minimal increase in performance if that. If spool was your concern, you'd be better off at that point experimenting with various other things like implementing a twin scroll to meet your goals.

A large majority of the Srt4 stuff I've seen, and from browsing various forums seems to usually be 50 trim t3/t4's, Gt3076r's or Gt35r's, and many of those seem to be using .63a/r hotsides. Big power stuff (like 500+whp) is usually a .82a/r. Actually, many of them have surprisingly similar looking dyno curves to 951's.

Todd, what was the question about boost pressure? Yeah, some of those guys run a good amount of boost. With more efficient motors, standalones, etc I've seen people run up to 25psi on pump gas, but that's the absolute highest I've ever seen on pump. Were you mainly asking because of the small hotsides? Running that much boost with a small hotside is somewhat of an attempt at futility. Something like a .63a/r with a 50trim or bigger turbo and running that much boost, the hotside is going to pose a big airflow restriction as it's physically too small for that kind of airflow volume. Because of that, even running lots of boost, the horsepower gains won't be too substantial however the motor will still make tons of torque. You can even see evidence of that with 951's. There are several people around here who have run say ~19-23psi on K26's, and they barely make any more horsepower than at ~18psi however they make insane torque (Nize's 951 comes to mind).

David Floyd

Here is a run, straight from the chip/board no tuning. 18 psi

shaheed

so you made it to the dyno again david? looking good, that thing must be running thru tires

gcb951

I would think having better spool up then hugh top end power would be alot more fun, especially on the street.

hosrom_951

Those turbos' are also dual ball bearing.