dave007

iTrader: (1)

I have an '87 turbo II that hesitates when you floor it. It idles fine. It seems to hesitate once you reach the limit of the TPS. I have a Super AFC in it and once the tps reaches 100% and I push the throttle past that point it will hesitate and then recover and take off. The car does great as soon as boost kicks in, but it has an extreme on/off throttle. The engine has 500 miles on it and is streetported. I have a Racing beat complete exhaust system, 720cc secondaries, lightweight flywheel, and a FCD. It runs 11-12 psi. The upper range is great, but the car lacks low end. It seems to have low vacuum at idle (13 psi) but I don't know what it's supposed to be on a streetported engine.

RETed

Check the resistance of the TPS at WOT - I bet it's over 6.0k&#937.


-Ted

dave007

iTrader: (1)

Ted checked TPS resistance at WOT it's only 4.8K.
Any other ideas?

RETed

Crap, I had to reread your original post...
Did you say *500* miles?&nbsp The engine isn't broken in yet - you shouldn't be doing any WOT, full-boost runs under after 1000 miles; who told you you could romp it at that low mileage?

Is the TB still stock on the engine?
Do you have the 720's tuned with the S-AFC properly?



-Ted

dave007

iTrader: (1)

Well I have to admit the break-in period was cut short on this engine. For those who read Grassroots Motorsports Magazine, this is the #65 car I'm talking about. I built this car in a couple of months. I wasn't able to get a title to put it on the road, and I didn't get the turbo built right until the Monday before the race and I was leaving to go to Orlando down that Wednesday. Anyway I went out on the interstate and ran the car real late at night/ early in the morning and got 400 miles on it. That's all I could do. I know I broke the rules.
Anyway, yes the TB mod has been done, and I do have the 720's dialed in.

This hesitation doesn't occur in the upper range, It's not any of the normal RX-7 hesitation problems. You don't have to drive the car to feel it. It seems to happen as soon as the throttle is pressed just passed where the TPS is extended all the way. It doesn't matter what RPM. It even happens when I let off and change gears. I can be sitting at idle at hit the gas pedal about half way and the car will stumble before it revs up. The car also lacks low end power, If I try to take off normal (let the clutch out at about 1100) and try to go, the car has nothing until the turbo kicks in. Also I only have 13 pounds of vacuum at idle (750-800). But if I rev it to 1200 or so vacuum increases quickly to about 18. To me this is sounding more and more like the TPS, but I ran all the checks that are in the book and it seems to operate smoothly.
Thanks,
David

RETed

You guys were the ones with the blown clutch???


Uh, this explains everything...you can't romp on it under 3,000RPM or the car will hesitate badly.&nbsp This is a function of the huge amount of air that the engine suddenly sees cause you removed the other set of throttle plates.


-Ted

dave007

iTrader: (1)

No, we're the ones that had the car come off the trailer and pass us on I-95. The car ended up going through three fence posts and hitting a tree. I have a dual friction centerforce clutch. It works good.

Is there anything I can do to stop the hesitation. Is the TB mod a bad idea?

RETed

Oh crap, then you're the gold one?


Yeah, drop the stock ECU and go with a stand-alone EMS like a Haltech.&nbsp The TB mod forces you to use the gas pedal smoothly under 3kRPM.&nbsp Else, keep all abrupt throttle changes above 3kRPM - it's a trade-off...


-Ted

dave007

iTrader: (1)

Man, I can't get the quotes to work so I'll just use the quotation marks.

"Oh crap, then you're the gold one?"

Yep that's me. We spent Thursday pulling sheet metal away from the engine. We found a couple of guys that drag raced RX-7's within minutes of our hotel and went to there shop. They saw the car and said there was no way we would get it back together. But we worked all day and they ended up giving us a radiator and oil cooler. Then we went to the other shop and bought a fan and fan shroud for $28. Before we left the shop we found a piece of muffler pipe in the dumpster about the same diameter and thickness as the now non existent cross member and the owner welded it in for us. About 25 zip ties later the oil cooler, wiring harness, coolant over flow tank, and other items were reattached to the car.

I have another question about my car.

I have no power until I get boost. Is this because of the TB mod? And I only have 13 pounds of vacuum at idle. Is this acceptable on a streetported engine?

-David

dave007

iTrader: (1)

Man, I can't get the quotes to work so I'll just use the quotation marks.

"Oh crap, then you're the gold one?"

Yep that's me. We spent Thursday pulling sheet metal away from the engine. We found two different guys that built RX-7's for drag racing within a few miles from the hotel. We went to the closer shop and when they saw the car they said there was no way we would get it back together. But we worked all day and they ended up giving us a radiator and oil cooler. Then we went to the other shop and bought a fan and fan shroud for $28. Before we left the shop we found a piece of muffler pipe in the dumpster about the same diameter and thickness as the now non existent cross member and the owner welded it in for us. About 25 zip ties later the oil cooler, wiring harness, coolant over flow tank, and other items were reattached to the car.

I have another question about my car.

I have no power until I get boost. Is this because of the TB mod? And I only have 13 pounds of vacuum at idle. Is this acceptable on a streetported engine?

-David

soccerguru16

maybe you should give me your turbo and i'll give you my 84 GSL that needs paint. sound good?