My Rex boosts nice and quick but as soon as I hit 3800-3900 it feels like I hit a wall and the powers gone. I can keep revving but it doesn't feel like im going any faster.

I did just install new injects and put on block off plates and have been fighting an overheating issue for some time now.

Any ideas?

 

So, you lose acceleration (but can still rev) at around 3800 rpms? Sounds like a slipping clutch to me, unless I misunderstood

 

Do you have an aftermarket boost gauge?
boost controller (manual, electronic, etc.)?
Do you know what you are boosting at?
Do you have a FCD?

What are you using to control your fuel? It sounds like you are going really rich when your upgraded injectors are coming online.

 

No I'm sorry, I should have explained it better. You can feel the car really pick up momentum until about 3900 rpm then it feels like you just hit resistance. It doesn't feel like its producing much power. Maybe I should video tape it.

No I don't have anything else besides whats listened on my signature bellow.

 

Like your secondary injectors aren't engaging?

 

If they did that your AFRs would start to go very lean, right?

 

Check your grounds: http://www.aaroncake.net/rx-7/grounding.htm

Also, how much boost is the car producing when it cuts out? You may be hitting fuel cut.

 

He said he felt "resistance" though... isn't the feeling of a fuel cut much harder than that?

 

Considering that your secondaries kick on around 3800 rpm with the stock ecu. I would suspect that is your problem. The stock ecu is programmed for 550cc injectors, not 800cc injectors, so I'd say you're super rich when they come online.

I'm not 100% positive, but I would say that you are in need of a rtek upgrade, or some type of fuel controller. A wideband and an aftermarket boost guage would also be recommended.

I'm fairly sure you would know if you hit fuel cut from over boosting. It really feels like you hit something with your car. I hit it once while adjusting my manual boost controller, and immediately found out why it's referred to as "hitting a wall".

 

I can see this causing the resistance he's experiencing, but it wouldn't be that bad with 800's would it? If the stock ecu's transition is already half crappy then I can see the effect being amplified, but 800's shouldn't "stop boost" in the secondary transition. Can you confirm that your boost in fact stop when this happens?

A video might be beneficial.

 

Silly question, but the 800cc injectors you replaced your secondaries with are low impedance injectors right?

 

I'm just not sure as I have never hit the fuel cut before. But do you guys think I could actually create enough boost at 3900 to actually create a fuel cut situation? I thought the turbos don't even start boosting until 2700.

Your very right thought I do need a real boost gauge, it would shed a lot of light on the situation. Moneys just tight but I'll see what I can come up with real quick.

 

Sorry lunch I didn't see your question. I'm sure they are but I never checked with an meter so I'll get on that too. Actually I have the box so I could call the company real quick.

 

maybe i can check it out for ya. i live in atlanta.

 

3500-4000 RPM is where you're most likely to have a big boost spike, so fuel cut fits. An easy way to check it is to rev the engine with little throttle. Keep it out of boost, and take it up towards redline.

 

Sounds like fuel cut alright, for one reason or another...

I had similar symptoms before i checked my tank and realized the horror that 20+ yrs of varnish can create.

 

@SirCygnus if you got a FCD that could eliminate a lot of the guess work in about 2 minutes

 

screw that. i dont deal with half assing ****. go straight up stand alone and eliminate 90% of every single problem that could ever occur.

 

fuel cut or a severely clogged cat.

when my cat was dying it gave similar symptoms like it would hit a brick wall half through the RPM range, the cat will make a loud hissing sound under the car if it is failing and the tailpipes will be a bit on the quiet side(the engine will also run hotter against the backpressure), if you don't have a cat that refer to #1.

 

Yea stand alone is nice but I don't have the cash to buy a haltech right now. I need to be realistic and get this thing road.

 

I have a suggestion. Drive your car up past 3800 without boosting (less than half throttle) and with a stable amount of peddle to see if it bogs down when crossing the 3800 mark. That should help figure out if boost or the secondaries are the problem.

 

I drove it today for about 30 minutes. I really think you guys are right. Its the fuel cut off. I can rev it slowly past the point no problem.

Worst part is the overheating. I'm not even running a thermostat and my RX7 has this special feature of turning water into chocolate milk. I think my water jacket is clogged up with garbage. I keep flushing it and it keeps turning it brown.