Hi I´m Patrick from Germany
last year i bought a ´87 FC Turbo II Coupe US-Spec .
When I drove home on the Autobahn and i reached about 140 mph
the engine interrupted like reaching a rpm limiter.
I fixed a few problems with the engine like leaking air hoses, but it still limited.

I have to say I do not often go for top speed, but yesterday I tried again, by the time I did some mods.
And now I saw when I reach 140 mph the boost slowly decreases and drops to 0 on my gauge.
It was really soft and not like a rpm limiter but like a speed limiter as in many German cars at 155 mph.
So I lifted off and floored it again, but the boost droped again after a short time when reaching 140.

Is this a known issue ?
I didn´t find anything about speed limiters in any RX7´s.

I assume it has something to do with the 2 additional throttles that are vacuum controlled. But why should they close when reaching 140, the other gears can be reved out so its not rpm related.

I already had the feeling that they 2 throttles close when trying to drive constant 100 mph because I had to push the padle more and more to hold the speed.

Greets from Germany , Patrick

 

No speed limiter on a US spec FC

You probably hit boost limit

 

All you should need to fix that problem is a Fuel Cut Defenser, if not, then ????

 

this is a false statement.. my old AT car with a 5speed swap would not let me pass 120mph. changed ECU to a 5speed ECU i hit 137 same car same tank of gas same everything. have not tried hitting max with my TII yet.. still got NA drive train..

 

as far as i know US Turbos, S4s's anyway have no speed limiter, i had mine up there a good few times, it just keeps climbing, and i looked into this before, IceMark knows his stuff and i would be sure he was right even if i didnt know, i can say for sure about the N/A's i never had my N/A up that fast

 

According to all of the official road tests I have read (road and track, etc.) the top speed is drag limited, meaning there is no speed limiter. I thought it said the top speed was in the 160's, but that just doesn't sound right thinking about it.
That said, its possible that some euro spec cars were speed limited, but thats a wild-*** guess.
Also, I've gotten my NA up to 145 on the speedo and there was no speed limiter.

 

ive had mine to 125 and it was still pulling pretty hard, but i didnt want to go any faster considering the alignment was causing it to shake like crazy

 

there is NO speed limiter on north american TII's. Period!

On stock and near stock cars, the limiter is wind.

 

I dunno, I've never had my car that fast, but at 140mph that puny stock turbo is probably having an asthma attack

 

Hm , I have a FCD , and this time it was not a Fuel Cut maybe the other times before.
Just the boost droped to zero so i had a N/A engine, it was a very smooth transition.
I really have no idea why this happens at 140.
As I assume the secondary throttle plates may be the cause, I will check all vacuum lines or maybe remove these plates like here:

http://fc3spro.com/TECH/HOWTO/TBM/tbm.html

Have some of you done this before.


Or maybe I just disconnect the vacuum line of these plates so they should always open with the main plates....

Patrick

 

Well i have a j spec series 5 and although the speedo stops at 180 kmh it keeps climbing, that was at about 4500-5000 rpm in 4th gear and i only took the car to 5500 in fifth and it was still pulling hard definetly no limit there

 

Check the TPS...
I bet the max resistance is over 5.0k at fully open?


-Ted

 

Just tested , fully open about 4.5-4.6k

-Patrick

 

Darn.

Try pulling the spark plugs?
What color are they?
Black black or white?


-Ted

 

......i wish i could drive the autobahn....

 

Yeah same here. I had my TII up to 135 once no problem when it was stock, but i was afraid to go any faster because our police officers frown upon such behavior.

 

what has this got to do with it? i thought the TPS could be anywhere from 4.0-6.0k ? if its reading over 5 dose it mean you car wont go as fast?

 

I dont really understand what you mean, but I dont think its a ignition problem,
as the car ran smooth at 140 there just was no boost. It was just like driving with half the pedal down, earlier it was like a limiter really frightening.
It was just the 3rd time I tested this.

Maybe if I drive the Autobahn tomorrow again, I try to take a little movie with my handycam.

-Patrick

 

is there a chance the twin scroll mechanism doesn't work anymore, choking the turbo?

 

We've run into this problem before.
Trust me.
Actually anything over 5.5k-ohms is suspect.


-Ted

 

It might not be...
Spark plugs could indicate what is actually wrong - the effect.

If they are BLACK, then the engine is running too rich.
Too rich will cause boost to drop.

If they are WHITE, then the engine is running too lean.
Too lean will cause power to drop...


-Ted