Take The "Spool Test"

[mike9146]

It occurred to me that since many people who are either new to DSM's, or are planning a turbo upgrade like to ask the ubiquitous "When does it spool?" question, I figured it was time for a standardized test that people could take to at least partially answer the question. What I suggest is this:

1. Set your BC to 15psi or more. (If you can! If you can't due to lack of supporting mods, you're probably running a stock turbo anyway, in which case, we really aren't hurting for data on it, if you know what I mean.)

2. In 5th gear, use the brakes to control the acceleration of the car. Start at a speed where your RPM's are less than the RPM where your car will hit 15 psi, and gradually increase your speed until the needle swings to the magic mark. (In addition, if you feel like telling us at which RPM you hit 20 or more psi, we'd like to know that, too!)

3. Come back and give us your results. Please list at least the following information:

Turbo/spec/trim/clip/porting/etc.
Exhaust Manifold
Exhaust System DP/TP/Cat/Catback
Intake Mods
Any other info you want to include that you think might effect your results.

Any questions? Okay, "Let's Get Ready to Spool!"

Mike C.
'92 AWD

 

[mike9146]

Big 16G ported/clipped 10 degrees.
Ported 2G manifold
"Custom" 2.5" DP, 3" Testpipe, 3" Catback, Magnaflow "Staright Through" Muffler.
2.5" UIP/Stock SMIC/1G MAS with lower HC removed/K&N filter

15 psi@ ~3050 RPM on SAFC

Mike C.

 

[larryd]

im not sure what you mean use your brakes to contrl your speed.. you just mean put it in 5th gear and floor it and see how long it takes to get 15psi.. Ill do that when I get the AGP L2R but on the Big28 it was around 3200

 

[mike9146]

Use the brakes to spool the turbo. "Power Brake" so to speak. You want to be at WOT at the point where the turbo hits 15 psi. We're trying to eliminate all other variables such as time, gear, etc, which make "Full Boost" RPM difficult to measure. So, for example, if my car will only make 5 psi at 2800, use the brakes and the throttle (floored) and "creep" up on 2900, 3000, or what ever turns out to me the "magic" number. Sorry for the poor explanation.

Mike C.

 

[larryd]

ie never power brakes a manual car so I haevnt a clue what your tlaking about it, but its all good

 

[mike9146]

I'm not sure why this is so complicated, but I'll try again.

1. While cruising along at 55 MPH or so in 5th gear, simultaneously push both the gas and the brake pedal, and "hold" the car at a steady speed, with the throttle to the floor.
2. *Gradually* release the brake, allowing the car to creep up one or two MPH at a time, until the boost gauge starts to move. Continue this until you reach a speed where the boost gauge reads 15 psi. Note the corresponding RPM. Write it down, post it.

 

[larryd]

i understand what your sying now but wouldnt that burn up your brakes?

 

[mike9146]

I don't know about your car, but my car goes from 5psi to 15 psi in a span on about 200 RPMS. If your burn up your brakes with engine torque in 5th gear using mostly 5-10 psi of boost for less than five or so seconds, it's time to take a hard look at your braking system!

Mike C.

 

[OMN_DSM]

Isn't easier to just floor it from 50 in fifth gear and get the data from there?

Mike

 

[mike9146]

Well, that would depend of where you think you make 15 psi. I can't believe that most DSMers don't at least have *some* idea where their boost gauge "takes off" in 5th gear. I mean, these cars go from "barely accelerating" when off boost in 5th gear, to "hold on" when the turbo hits. You be the judge at what speed you start at. That's the whole point of the test- to find out at what RPM (or speed in 5th gear if you like) your turbo makes 15 psi of boost. It really isn't rocket science.

Mike C.

 

[OMN_DSM]

Your right, it isn't rocket science, but your instructions are a little complicated for the simplicity of the test.

All you need to do is be at speed that is below instant spool in fifth gear and floor it and see where your at.

mike9146, What color is your car, I may have seen you around

Mike

 

[mike9146]

"All you need to do is be at speed that is below instant spool in fifth gear and floor it and see where your at. "

That is the idea, but if you have a modded car, it's hard to get an accurate number with the car accelerating. Hence, using the brakes.
My car is Electric Blue with stock wheels, FWIW.

Mike C.

 

[RocketDSM]

I would be more worried about my clutch than my brakes. If I'm not letting the car accelerate, but forcing the engine to rev, without shifting...that spells burnt clutch to me. No thanks.

 

[Enigma_Man]

Hehe, Mike. I understand exactly what you're saying, and the reasons for it, if that makes you feel any better

I'll have to do that when I get a turbo on my car again. I'll have a brand-spanking new 16g, and basically 0 other mods

For the people that are hard-of-understanding, Mike's basically proposing a way to dyno the car on the road. Holding the brakes while flooring will heat up your brakes, yes, but your clutch will be just fine, and if it does fuxor your brakes, then yes... you need better brakes if you're just doing it for a few seconds. This will allow you to get a more precise reading, and your turbo will spool lower, because it takes time for the turbo to spool, the rpm's will be higher if you don't power-brake where you hit 15 psi.

-Jes

 

[RocketDSM]

Well, I tried. Going under 55 on a California freeway is almost impossible. Anyway, I got it down to 3400 at the lowest. Usually, I was 3800-4000.

Blitz Filter, Full MAS, Injen Pipe, Small 16G, RC Throttle Body, Extrude Honed Intake, Ported Exhaust Man & O2, Apex N1 Cat back.

Hopefully, I'll be getting a DP soon and this will come down a bit.

 

[RetardedAWD]

With putting it in 5th gear and mashing the breaks and mashing throttle at the same time creates the same situation(ie going uphill in 5th @ a low rpm throttle floored) in which you are inviting detonation.
Think about the gears in your car like gears on a bicycle, the higher the gear the harder it is on your legs to pedal. The same principal applies here. Your going to make it really easy for your motor to get one GOOD knock thats going to be putting tons of pressure on your bearings, rings and ring lands, rods etc.. when a knock occurs cylinder pressures spike through the roof..

Just throwing in my 2 cents.

 

[Tee]

You are Sofa King We Todd Did.

Except you mike, your cool, and whoever the other guy was that figgured out how to drive a car.

 

[NDgsx]

Mike, you should make all the tests start a specific rpm. That will show the true boost threshold. If you punch it at 2700 then lag and accel enrichment will change the rpm point.

The thing this test will NOT show is true lag time. That is the period of time it actually takes the turbo to make full boost. Too measure that time you start at an rpm above the boost threshold. Problem with that test is few people have a map sensor and their car and even fewer have a way to accurately log the time.
The boost threshold rpm and lag time aren't directly related. Riding in Shawn's car (20g for the non nwdsmers) up Snoqualmie pass I noticed that when he punched it above 4k the actual time it took to get full boost was not that much different than Matt's big 16g. The real difference was the boost threshold rpm. If Shawn kept his car at a higher rpm lag was not a issue at all (the afr no load correction problem makes 3-4k a PITA though, Shawn's rpm point might not be that much different than Matt's if it was set up just for WOT).

btw I've been looking for tires, but business has been slow this week. There are always four brand new yokohama AVS sports if you want them . I'm just going to get 17s for the street next spring and put some race tires on Matt's old 16s, I don't need the extra set of yokos.