what's wrong

Hey, I have a 91 MR2 turbo with an HKS Hi-Power exhaust, k&n filter, greddy intercooler, and run 14 psi with the greddy profec b spec II boost controller. I also replaced the cap, rotor, and wires with toyota parts and replaced the plugs with NGK's. I just did a compression test and each cylinder was around 185. The problem is I only run low 15's in the quarter mile. Any suggestions on why that is?

Thanks in advance

What rpm are you shifting at?
What's your 60' time?
What's your mph at the end of the track?

I shift at 5500
60' was 2.057
mph was around 89

You should redline 1st ... 5500 is about right for the CT26 turbo for the rest of the gears.

Your 60' is fine. It is possible to nail a 1.8 or 1.9 with a stock MR2. It takes practice and you may want to drop your rear tire pressure depending on what you had them at.

Your mph is very low for your level of mods which means you are down power. What did you gap the plugs too? What octane fuel are you running? What elevation was the track at? How hot was it outside?

the plugs were gapped at .28
i run 93 octane fuel
I'm not sure about the elevation but I think it's low
the temperature was about 78 degrees

How fast do you shift? What kind of tires do you use? How is your alignment? How heavy and what size are your rims and tires?

I try to shift as fast as I can. The tires are some kind of Firestone something, not sure. I bought the car from an older man who wasn't using it for any kind of racing so i'm sure they aren't the best performance tires. Haven't had the alignment checked but the car drives as straight as can be with no unusual tire wear. I still have the stock 14 inch wheels and stock tire size.

I sure hope you mean he gap was .028", not .28" :)

Elevation, temps and fuel check out.
I don't think tires are the issue since you managed a very respectable 2.0 in the 60'

Somewhere, somehow you are down power.
Do you have excess weight in the car? (like an extra 200 lbs of stereo equipment or something?)

sorry, I did mean .028"
The only modifications that I have done to the car have been the performance mods. The only additional weight in the car would have been me and the spare tire. I weigh 165 lbs and I wouldn't think the spare tire would slow it down that much.

No, the spare and your body weight are not a big deal. I just wanted to make sure you did not add a 100 lbs of subwoofers and 15"s :D

So, we are back to your car being down power.
You should be easily trapping well over 90 mph, so something is up.

Is your clutch slipping?

No, the clutch grabs like it should

is your suspension still good?

yea the rear end plants on take off with no wheel hop

you ARE driving an mr2 right? :D

yea that's what it says on the back of the car :biggrin:

that just means that your spring rates are correct for the car... how old/soft is the suspension?

well it looks like its the original suspension components but it still feels firm

An old and worn suspension would be a benefit in a drag race.

Again, your car is down power for some reason.
I would start with checking codes, make sure you do not have a some gremlin stored in there.

I'm not exactly sure but doesn't the MR2 use flash codes or do I need a scan tool. Also, how often should I replace the NGK spark plugs that are one step colder? I think they're called BK7RE.

You can use either the NGK 6097 or the 5030s (one of them are the BK7RE). I would suggest changing them every 3000 miles when you do your oil.

I am changing them much more often but I am beating the hell out of them :)

The MR2 stores codes and you can check them by looking at your check engine light. In the engine bay there is a little diagnostic box (trunk/engine firewall). You need to jumper TE1 to E1 (paperclip is fine or a short piece of wire).

Then watch your check engine light. If it flashes steady, you have no codes.

Otherwise it will flash in code. There may be several codes and they continually repeat so don't worry if you miss one. Long pauses are between codes. Short pauses are between numbers.

So:
5 flashes, short pause, 2 flashes, long pause ... and it repeats, that is code 52 (knock sensor).

Where can you find what all the codes mean? is there a book you can buy or something?

http://www.mr2-tech.com/bgb/mechanical/volume1/efi_system.htm

Click "Diagnosis System"
... then make sure you are looking at the correct engine numbers (3SGTE, not 5SFE) :)

Well I just checked for codes and there weren't any. But I do need to change the plugs since I've had them for over 3000 miles.

Let us know what the plug tips look like.

The plug tips had some carbon around the edge's. The electrodes looked fine. The plug wasn't beat up or anything. All four plugs were almost identical.

hmmm ... the mystery continues.

If it were my car, I would:
1. Check and double check that I do not have a boost leak (do you know if your exhaust comes out heavy black at WOT?)

2. I would verify that I am making and holding max boost to my shift point.

3. Spend $40-$50 for 3 pulls on a dyno to see what kind of power I am putting down and take a peak at teh A/F ratios to make sure everything is cool.

Yeah, I've been thinking about getting to a dyno as soon as possible. I'll also check for a boost leak and that I'm holding max boost until I shift. I'll try to get it done as soon as I can and let you guys know what's going on.