how much boost?

Hello all I have a 91 mr2 with a 95 jdm 3s-gte motor. I have all the JDM parts swaped in the car. I am running a full 3inch exhaust and cold air intake. The only thing on the car that is not JDM is the frame. I just bought the greddy profec boost controller and I wanted to know what is the max boost setting that I can set with out blowing anything. I have a race with a 3rd gen rx7 tt comming up and I need to win. Any info would be great.
thanx

I see no problem with you running 15-18 psi. You might need to plug the MAP sensor to aviod fuel cut, but im not sure on the JDM motors. It has the CT20B correct? I heard not to run too much boost on that turbo for a long period of time.

You heard that because its a Ceramic wheel...

I wouldnt recommend anything about 15 PSI without intercooling. Also dyno tuning of your AFM afterwards is a MUST

I see no problem with you running 15-18 psi. You might need to plug the MAP sensor to aviod fuel cut, but im not sure on the JDM motors. It has the CT20B correct? I heard not to run too much boost on that turbo for a long period of time.

from what i've read, the JDM 94+ are gen III engines. if you disconnect or plug the map sensor, the engine will not run. the gen III ecu's use the map sensor to calculate fuel/ignition instead of an air flow meter.

Word. I know it ceramic, thats why I posted not to run much boost. Gen lll motors do not have AFM's and the car is intercooled stock Lachean. What do you me by dyno tuning your AFM afterwards, and intercooling it?

There is no way to tune an AFM.
And dyno tuning is not a must.

I also would not run over 15 psi without either: race gas, upgraded intercoolwer or water injection. Personally, I use all three and run 22 psi out of a bigger turbo :D

Not to burst your bubble, but I would not be optimistic about the race with the Gen3 RX7 (that is the last body style - correct?).

oh, the gen III engines also do use the CT20B.

i'd listen to jek though.. people don't make 308rwhp by not knowing what they're doing.

if i were you, i would look into a decent water injection setup. do a couple 3rd gear pulls on the street with it turning up the boost REAL slowly and listening/feeling for knock or the ecu pulling timing because of knock (you likely won't hear it).

i'd also base the max boost setting on what the other guy is running. you both weigh about the same (FD's are 2700-2800lbs), and if he's stock, just turning it up a little should be enough. if he's heavily modded.. well.. just don't race him for money.

I agree, if you're gonna mod your car in limited time like this, the rx7 would prob do the same. Now i dont know too much bout RX7's but i think they should take bolt on's pretty good if not better than you. Considering it comes out of the box a monster already, and those babies almost has no turbo lag and can boost even a TRUCK turbo, I'd suggest not racing the RX7 unless you know its fully stock or at least with minimal mods. On the other hand if you dont care bout your car and you MUST win this race... A quick fix might be to spray. THATS ONLY IF YOU DONT CARE BOUT YOUR CAR. not saying that NOS is will blow your car, but for someone to use it desperately to win a race will prob damage the engine. just a thought.

The 3rd gen Rx is not heavily modified. He has a couple boltons and he put up his boost. He is running low 13's. Ive been monitoring my Boost and at the stock setting it seems like im pushing between 15-16 pounds of boost at 5500 rpms. I will be using race gas, 106 octane. what do you guys think??

If he is running low 13s, I would say the cars are closely matched ... but I would say the favor goes to him since he has track experience in that car.

Getting an MR2 off the line is not the easiest thing in the world to do. There is a fine line between lagging/bogging off the line and spinning the tires.

Do you know your shift points?

If he is running low 13s, I would say the cars are closely matched ... but I would say the favor goes to him since he has track experience in that car.

Getting an MR2 off the line is not the easiest thing in the world to do. There is a fine line between lagging/bogging off the line and spinning the tires.

Do you know your shift points?

I totally agree, i drag raced my friends EVO from stop and i have to admit it was one of my first races. Even though he bogged launching his car, i had just an equal share of my troubles. Most of the time i would peel more than id expect. I dont think that my problem is feathering the clutch but rather precise throtle control on take off. So before i go off on the subject... the point is to know your car better and see how much throttle u can push gradually so there wont be too much of a peel.

I can honestly say that I have a little experience. I took out a 5.0 club who underestimated me, but yesturday I did a couple of quarter mile runs and I ran a flat 13. I kept on messing up my launch. I was lagging and launching at 2500 rpms. when I launched at 3000 rpms my tires spun like crazy what RPM's do u guys think I should launch at? By the way I was just challenged by a guy claiming he had a j30 with a stock 300z engine. What do u guys think about that??

Where were you doing runs?
I am guessing G-Tech runs? There is no way you were running 13.00 with the mods you listed (unless you have the CT20B turbo).
An expereinced driver could not hit 13.00 with your mods.

With your mods and perfect driving you are looking at 13.3-13.5 at 16 psi of boost.

Your launch sweet point will probably be around 5500 rpms, you should shift around 6600 rpms in 1st gear and around 5500rpms in the rest of the gears. (unless you have the CT20B turbo, not the CT26).

I have no comment on your other "challenge".
As funny as this may seem, I am really not that interested in beating someone else. I go to the track for my own enjoyment and improvement.
There will be always someone faster. So what? :)

I have the CT20B turbo, I did a run today just to observe my boost meters and I think the most psi I can push is about 20 because at 22.5 the turbo lost a little power and I heard a knock. How much is the difference between the two turbo's???

The ct20b is significantly better than the ct26.
You should be able to shift at redline with that turbo and a 13.0 flat is much more reasonable.

Well with that in mind do you think I could break 13 seconds. I felt like i botched up the launch with that run. Do you think a short shifter will help? Do you think the boost levels will change since I have the better turbo?

To quote myself:
"I also would not run over 15 psi without either: race gas, upgraded intercoolwer or water injection. Personally, I use all three and run 22 psi out of a bigger turbo "

Running a 12 sec pass is not going ot be easy. The ct20b and teh ct26 are roadcourse type turbos ... not designed for drag racing ventures. You can get a ct20b in to the 12s (there is one in the 11s), but it takes perfect driving and supporting mods.

With good driving you should be able to hit low 13s at 15 psi.
The biggest way you can improve your ET ... is to practice.
You will gain as much as .5 from practicing, IF you are learning nad improving your driving.

Your launch sweet point will probably be around 5500 rpms, you should shift around 6600 rpms in 1st gear and around 5500rpms in the rest of the gears. (unless you have the CT20B turbo, not the CT26).

Wow 5500 rpm launch? wouldnt you peel too much on launch? And can you explain the reason why shifting at 6600 and 5500 is better than shifting at redline, im not too sure how that can maximize your speed. Well on another note, i dont drag too much anymore cuz i heard a mr2 launch is bad for the car, since we has lsd and all that weight on the back tires it might be a lil too much for car to handle, is this true? Well untill i reinforce my axles and rods , im not launching my car.

Wow 5500 rpm launch? wouldnt you peel too much on launch? And can you explain the reason why shifting at 6600 and 5500 is better than shifting at redline, im not too sure how that can maximize your speed..

well, i'm a road racer, not a drag racer, but when we do standing starts, you don't do them by dumping the clutch and modulating the gas, you "dump" the gas and modulate the clutch. higher revs keep it from bogging.

as for shifting, the CT26 runs out of breath at about 5500rpm. there's little to gain by staying in gear after the motor has stopped making power. you will accelerate faster if you drop the rpm back down to a range where the turbo can still make effective boost.

yes but even if you were to modulate the clutch wouldnt it still be very hard to keep the tires from peeling? i mean controlling such a launch is very hard. I say ease the cutch at 3000 and eliminate the error percentage. and besides clutches arent cheap.

Wow 5500 rpm launch? wouldnt you peel too much on launch?
With the OEM turbo you may be able toget awa ya little lighter ... 4500 -5000 rpms. Yes, you would peel out if you dump the clutch. We are talking about the finesse of launching, not dumping a clutch. I would refer to it is a "quick-slip, dump". Basically I slip the clutch very quickly and got WOT/dump when I feel the "tug" of the car.

And can you explain the reason why shifting at 6600 and 5500 is better than shifting at redline, im not too sure how that can maximize your speed.
You want to race in the power band. The stock CT26 turbocharger on the MR2 has no powerband above 5500 rpms.
Well on another note, i dont drag too much anymore cuz i heard a mr2 launch is bad for the car, since we has lsd and all that weight on the back tires it might be a lil too much for car to handle, is this true?you're kidding right? Everything you listed is exactly why the MR2 IS a great car to luanch. LSD = traction. Engine over the power wheels .... in Japan, the MR2s are classified with the AWD drive cars because their launches are so great.

Well untill i reinforce my axles and rods , im not launching my car.The only thing to be concered about is breaking the CV Joints ... and that tends to happen if you have over 300 rwhp. I broke them once. ATS Racing offers an upgraded CV Joint (which I now have). No problems here. I slip/dump my race clutch at 6000 rpms!
yes but even if you were to modulate the clutch wouldnt it still be very hard to keep the tires from peeling? i mean controlling such a launch is very hard.
No one ever said it was going to easy ;)
I say ease the cutch at 3000 and eliminate the error percentage. and besides clutches arent cheap.
If you ease the clutch at 3000 rpms, yo uare going to bog, your turbo is going to lag and it will take an eternity to get off the line. You wll in act increase your "error percentage". In a dragrace I would rather have some wheel spin off the line than have my turbo lag.

Yes, clutches aren't cheap. Neither are tires, axles, etc ... if you are going to race, yo uare going to eventually break things. There is no way around it. If you are going to baby the car off the line, what is the point in racing?

You will never see the potential of your car unless you are willing to explore it.

Generalized formula for figuring out shift points:
Lower gear ratio / higher gear ratio X RPM at peak Torque = Shift RPM

Applied to the STOCK CT26 Turbo:
Using the same formula for a stock CT26 MR2, I get shift points:
1st --> 2nd = 6595 rpms
2nd --> 3rd = 5643 rpms
3rd --> 4th = 5595 rpms
4th --> 5th = 4915 rpms

That is true regardless of power output unless you change the peak torque point.

Notice how both of these ct26 cars with varying mods have the same peak torque point:

276 HP CT26
http://www.turboforum.net/dyno/images/mattjenkins/dyno276.jpg

161 HP CT26:
http://www.turboforum.net/dyno/images/averyd/redmr2dyno.gif

Same turbo, same shift points :thumb:

Wow , i never expected such a detailed answer. Thanks alot hyde, it was very informative. I have to admit i do feel a little safer about launching however i am still a bit skeptical, probably because im not used to the hard shifts on lsd. It feels like i snapped something everytime, but thats just me. So with that being said i end this post since hyde has absolutely given me no more room for questions. Dman you hyde!!! i will stump you one day..... one day!!!!!!!! :banghead:

I have to admit i do feel a little safer about launching however i am still a bit skeptical, probably because im not used to the hard shifts on lsd. It feels like i snapped something everytime, but thats just me.

are you sure you're shifting properly? a good shift is heard but not felt. the only time i ever feel my shifts is when i do them slowly..

maybe im not doing it correctly, but im still learning.