Cheuk in Seoul

After reading some of the post, I decided to take my car on some highway runs in 5 th gear and try to measure boost response.

This is a large street port and RX6A... numbers were measured on a AVC-R

Onset of + boost @ <2000 rpms... almost instant.
10 psi @ 3000 rpms
14.7psi @ 3550 rpms

Seems to build slowly to 10 psi and climbs quickly to where I have the wastegate / AVC-R set at 1 bar.

Anything else boost this quickly? Maybe T04E?

Silver7

I have a T04E with 60-1 comp wheel. I have tried two different sized compressor housings, a .6 and a .7 A/R. The turnine housing is a .96 A/R.

.6 --> 10 psi at 2800 - 2900 rpms, 15 psi @ 3400
.7 --> 10 psi at 3300 - 3400 rpms, 15 psi @ 3700

The .7 pulls significantly harder up top. I have found the same thing as cheuk, it takes a while to get 10 psi but once I hit 10 psi, 15 psi comes very quicky.

Eric Michel

Doing this test in 3rd or fourth gear would be more realistic and easier on your car.

Cheuk in Seoul

Yeah, I know but running in 5th gives me time to freeze the AVC-R display. Otherwise the dang thing spools so fast I would only be able to guess where the boost points are at.

The car is pretty slow at WOT in 5th gear below 2000 rpms.

fast13b

On mine the rpm's at which the different boost levels are reached are different in each gear, you might want to take that into consideration.

With my T-66 in 2'nd and 3'rd, I get 10 psi around 4000-4500 and 15 psi around 5500-6000 rpm. It doesn't accelerate worth a **** in 5'th. Want to sell it and get a 60-1.

~Jeremy

Wade

iTrader: (1)

Why don't you guys do this test in 3rd gear too so we can compare the results to some stock turbo setups?

Drive at 2000 RPM in 3rd gear, lift and get maximum vacuum for a couple of seconds, then floor it and start a timer. Stop the timer when you hit your max boost (and please indicate your max boost). Repeat for 500 RPM increments until you reach max boost almost instantly.

Example:
stock twins
12psi max boost
2000 RPM - < 3 seconds
2500 RPM - < 2 seconds
3000 RPM - < 1 second



5th gear would be good for comparing different single turbos, but it doesn't give a realistic representation of lag for those of us wanting to know if we could live with the lag of a single compared to twins. 95% of my driving is in gears 1-3... if I'm trying to go fast I'm definitely not flooring it in 5th and very rarely 4th.

Wade

Silver7

I can tell you right now without even doing the test that it will take me way longer than 3 seconds to get to full boost from 2K rpms, and I don't even have a big turbo!

Cheuk in Seoul

Now you want me to do what??
You know how hard it is to find a stretch of open highway in Korea?

Now I've got to look at my tach... start / stop a stopwatch and avoid the crazy Korean drivers... all at the same time.

OK.... next time I get back to the shop where I have the car stored, I'll give it a try....

Will counting... thousand and one, thousand and two be OK?

Seriously, What do you guys think is the best way to quantify a single turbo's lag and response?

jspecracer7

I thought a 60-1 wheel in a .7 a/r compressor housing is a T-04S?

Silver7

I am not sure what a T04S is exactly. I have heard different things but nothing really concrete. I am using an "on center" .96 turbine housing. I think the T04S uses a 1.0 tang style housing

jspecracer7

Yeah, I think that the hotside is a 1.0 a/r. I didn't think that the style of turbo housing didn't matter.

Anyone else want to chime in?

Silver7

I'm not sure what you meant by your last sentense but "on center" turbine housins come only non divided, while tang style can come either way. I believe the XS kit comes with a divided housing and divided turbine housing. I am sure about this though.

Eric Michel

A chassis dyno chart would work quite well. There is a new Dyno chart section in the photo gallery, post them there please

fast13b

I think that the bottom line in this question comes down to what will make your car the fastest. The answer lies in having the right turbo for the job... The amount of lag a particular setup has is secondary. What we are all looking for here I think is to gain the most area under the curve, that is what makes one car faster in a straight line than another. If we were to take two dyno charts and draw one line horizontal at an RPM like say 2000 and a line vertical at say 7500, then by following the power line past these two other lines to make a 'triangle' shape, we could calculate the area "under the curve" of each car. This is the amount of time in power. The car with more area will be faster, regardless of who has less lag or who has more HP. Just my thoughts...

~Jeremy

Wade

iTrader: (1)

Gordon and others,

Don't misinterpret this as me trying to start a stock vs. single thread. I'm just trying to encourage some people to gather some numbers that are meaningful to people like me.

It is undisputed that a large single turbo will give much more power, and it might make a lot more power even at low RPMs, once spooled. And of course, adjusting driving style probably makes the response a non-issue.

And Gordon, you are right, simply comparing max boost minimum RPM or the time it takes to reach max boost from a certain rpm is NOT the proper metric to compare singles versus stock turbos. This is just one factor when comparing the two (which happens to be frequently overlooked).

A dyno chart is biased in favor of singles. Dyno runs are usually done in 4th gear and the amount of time it takes to build boost is not clear on a dyno sheet. Though in some cases, you can clearly see where a very large turbo is spooling.

I wouldn't even ask about this if I had some locals with singles so I could drive their cars and get a feeling for the response. It's inevitable that some day my stock turbos will be bad and I'll be faced with a decision to switch to a single, and I don't want to be surprised by the feel.

Since these turbos are pretty much hopping by 3000-3500 RPM, I probably have nothing to be concerned about. I'd still like to have as many numbers as possible though.

Wade

Eggie

That's a great point, Gordon, and plenty of dyno charts show singles making more power at less boost. However, I think the lag discussion is more about drivability and powerband width than about which kit's faster in a 2000-RPM dragrace. With the FD's wide gap between 1st and 2nd, coming out of a corner at 3500 RPM in 2nd makes more sense than downshifting. The sequentials can be scary here, since the tires can break loose very suddenly at 4500. How does your T78 respond out of the same corner?