im working on an 87 rx7 turbo-2 that a friend of mine owns. we just installed a good size T61 turbo (.70ish compressor and .80ish turbine, i dont remember exactly) and it spools 15psi about 3500 rpm and the car runs good but just isnt that fast, i know its boosting and there is no leaks. it has 720cc secondary injectors with an safc2 and wideband to tune all at around 11 to 1 AFRs through the whole powerband.

it also has a fmic, 2.5in pipeing, most emmissions stuff removed, rebuilt with 3mm seals, any help would be greatly appreciated. thanks!

 

do you have after market exhaust or stock.. cats?? you just didnt mentin that stuff

 

15PSI with only 720CC secondaries???

I'm not sure if it's safe...

 

Sure it is...

 

Uh, no, thats not very safe.

 

yea, something very serious is missing here or someone is lying.

far as the lack of power goes, i would say it could be ignition related but it wouldn't net you a 11:1 AFR so refer to my original statement. a piggyback with that turbo is just retarded.

 

just out of curiosity couldnt you do 15psi on 4 720cc injectors though??

 

Possible, but why chance it?

 

4 720s is good for about 350RWHP, that turbo could produce more than that i would think depending on the trim of the wheel.

 

there is no cat, nothing should be clogged, its 3in mandrel bent. i can back the boost down some but either way its still slow. its about as fast as my 240 was with about 220whp, and i know it should be significanly faster than that. other than not being fast the car starts, idles, and runs perfect.

 

What is your timing map looking like?

 

honestly i have no clue. im pretty usesless when it comes to rotarys. i know most cars have a safe/knock/low octain map that they use when a sensor is messed up, how would i check for this?

 

Never mind.. YOu are on an SAFC. I was thinking of something else.

 

if he's running around 11's in his AFR's I wouldn't think it'd be fuel related. Why do you say it's "not that fast"? Have you been cruising around in a 10 second car lately, and this one isn't doing it for you?

How long does it take you to go from 0-60, or 0-100?


edit: Sorry just saw the 220whp 240.......SO, have you done a compression test?

 

Lets look at a few things here:

First he is using a T-61. Its the SAME turbo I have except I run a .96 AR exhaust housing. At 18 PSI, with 720 cc primaries, 890 cc secondaries AND alcohol, my IDCs were already hovering in the 90% range. Thats closing in on UNSAFE.. Furthermore, the volume of air that turbo moves is VASTLY more then a stocker. (and thats 385 wheel on my car). So how he is maintaining 11 AFRs is BEYOND me..

Second. Its an SAFC. There is literally NO timing control available for those power levels. Running those HP levels on an ECU with an SAFC is NOT ADVISABLE.

Third, the damage may already be done. 3mm apex seals WONT SAVE YOU. My guess is the motor is already toast...

Rat

 

after reading this post a few times, i think it really helped.. what if it ISNT getting that much air or allowing it to flow through just building to that pressure, like stuck throttle body plates or stuck ports. would that cause it to run ok, be at 15 psi and still be slow? ive always heard its the amount of max HP that a fuel injector is messured by, not the psi of a turbo (whatever its size may be) and that would explain how i got 11 to 1 all the way through the rpms with verry little tweaking on the safc2. any thoughts on this idea?

 

Well lets do some math (WEEE FUN!!)

You're stock ECU runs you injectors at about 58% duty. With the S-afc CRANKED up your max is 78% (and you apparently don't even have it cranked).

Now, with 500cc pri. and 720cc sec. at 78% - you can support MAX 280bhp....at the wheels....about 250. (according to rx7.com's fuel calculator) But assuming your "minor adjustments" were only 10% up, you only have enough fuel for 248bhp.

Now, there is NO WAY IN HELL that you can be running a t-61 at 15psi with only enough fuel for close to 250 to the wheels.(the 250whp number being if you had the SAFC cranked to the max) That turbo at 15psi should be putting down over 300.

As far as your AFR's go, how close n the WB probe to the motor? It should be mounted 36" from the exhaust ports......maybe that causing these ABSOLUTELY INCORRECT readings.

You're motor IS running lean if you in fact have this setup.

I would check your compression before doing anything else, you may already be near blowing a seal through that nice turbo...

 

the wideband is about 36" away, its calibrated correctly, and works perfectly. and yes, it is the setup i described EXACTLY. im not lying there must be another problem. if it was that easy i wouldnt be here asking about it. i will go check the compression today but i dont think thats it cuz the cars starts perfectly and right up, and runs and drives perfectly and pulls very smooth. hell i might borrow a digital cammera from somebody and take pictures for everybody here to prove that this setup is exactly as i stated it was. there has to be another problem. the motor has a street port done to it as well but im not sure to what extent, i didnt build the motor.

how do i know if all the ports are opening? ill test the throttle body today here in a few hours.

 

could have a boost leak, just enough to lose a significant amount of air but to create enough boost to give the impression that it should be putting down some serious power. i have seen some odd boost leaks that can allow for full boost on the gauge but the car is dog slow.

however.... if this is the case, once you repair that leak the motor WILL blow up once you drive it hard. why? because everyone in this thread has concurred that the fuelling is inadequate so this is your risk to do it up right before trying to fix anything.

 

What ports? its a 4 port motor....there are no aux. ports that "open" at xxxx rpm.

As long as the throttle plates are opening all the way you're good.

 

ok thanks, its hard to talk the owner of the car into getting bigger injectors when its not running right still but ill ask him. the WG opens at 15 psi but has a boost controller on it, its turned down all the way but i will just remove it fromt he system completely cuz i know that they will sometimes still restrict air flow just being inline. i hope the WG spring isnt set to high. i will look for boost leaks but the car is useing all high dollar intercooler piping, couplers and T-clamps so that should remove most boost leak problems. could a large vaccume leak of some kind cause this problem? i really am new to this stuff as you can see, but i do know alot about piston (mostly nissan/honda stuff) motors. thanks for all the help so far, this car might have the possiblitly of being fast still. thanks!

 

vacuum leaks turn into boost leaks under pressure so, yes, take a look at all the vacuum lines and UIM/LIM as well.

also take a look and be sure you are getting spark at each plug, it could be that one of the coils has failed.

 

i checked the spark and its good, replaced the plugs with new ones as well (i used all trailing ngk plugs)

what is "UIM/LIM"?

 

lol. UIM= upper intake manifold LIM= lower intake manifold..


gotta catch up on the forum lingo.lol j/k

 

maybe your fuel pump is falling on its face?