Rx7 is losing boost at high rpm and not sure why.. did 2nd 3rd and 4th gear pulls and exactly the same drop.. will hold 12.5psi btween 3-4000 but will then drop to 10 psi by the time i get to 6000. is it possible the boost could be leaking somewhere? I have checked bov and its not there so maybe leak in fmic??

related mods are:

hybrid turbo s5 with t04 compressor.
tial 44mm wastegate
microtech lt-8
660cc secondary injectors
front mount intercooler.
3 inch exhaust no cat

 

could be a leak, but most likely just the restrictive hotside. Here's an example. the BNR stage 4 hybrid has a 60-1 wheel with a .60 A/R T04B compressor housing and a ported stock exhaust housing. It can usually hold about 14 to redline. I have a full T04S turbo with a .96 A/R hotside, .70 compressor, same 60-1 wheel, and I've gotten it to hold 20 to redline (race gas etc)

 

Buy the time you hit the redline you're going to be losing boost. Just the way the stock turbo is. Between the heat and the restrictive hotside(compared to aftermarket turbos) it's going to happen.

 

^yup. stock turbo wether hybrid or otherwise will drop off in the higher rpms but I guess it could be a leak. If you aren't experiencing any other symptoms of vac leacks then i would say its just the nature of the beast.

 

Hmmm Sorry to bring back from the dead, but I'm having this exact same problem. But I made a different' hybrid t3/t4 internal gated and my s5 hot side, wastegate ported and what not. It pulls 1st, 2nd, and 3rd, and into 4th until 6500rpm. It acts like it's not firing or just stopped producing pressure. (This is WOT mind you) Once it hit's 6500rpm the car just hits a wall. Also 5th gear doesn't want to boost well at all. But it will on in and out depending how I play with the gas.

I made another hybrid previous to that, which was a T04e with stock s5 hot side. And it pulled to red line and had no problem going to 8k, even in 5th. (This the old motor took with it to the grave)

It's not a fuel cut, I have r-tek. My afr's are 11.1 - 12.1. It goes from 14psi to 5-10psi at 6500rpm in 4th only. I installed msd 6a on the leading, it was doing the exact same thing but in 3rd.

Sorry, to thread jack didn't want to make another one especially when the problem is the same thing I'm having.

Thanks, in advanced.

 

It could very likely be your TPS. I had a wall at about 6500 RPM as well and my TPS was bad. It doesn't matter that you have an Rtek, it still depends on the TPS to give correct values. I couldn't test it very well, a digital multimeter doesn't show sweeps well, and I couldn't get an analog one to work right. I bought a used one and that solved my problem.

 

Was this only in 4th and 5th gear? Or all the gears? 1st, 2nd, 3rd pull very well. All the way to red line and holding pressure. But once 6500rpm... only in 4th and 5th. I'll check out the tps regardless.

 

I think I couldn't pass 6500RPM in any gear, but it's entirely possible I didn't try it in 4th or 5th because of the speeds you're running at that RPM in those gears. Now that it's fixed, however, that may be another story...

 

lol. I don't believe it's my TPS, since I can pass 6,500rpm. But on a flip side, Now I can go past 6,500 in 4th and 5th gear. 4th gear pulls like it did with the T04E, but this time it holds to redline

 

I define 'hitting a wall' as the car lurches and refuses to accelerate AT ALL, won't even try to maintain its speed. Maybe that's not what you meant.

 

Hitting a wall. "Misfiring, but not detonation it. It would hold boost 13-14psi then right then 6500rpm hit, boost dropped to 5-10psi and fluctuate for a second and stay at 10 pounds and not go anywhere. It's basically I hear the turbo spool, then no more spool noise, and I thought it was my spark blowing out. (So I installed msd 6a, mind you it was doing this in 3rd gear and up before. But since I installed the msd it moved on to 4th gear.)

It's basically going from pulling pulling, no power, no power. It doesn't matter if I shift into 5th where I'm at peak boost 5400rpmish. (I get full boost at 4,000rpm, I have a .60 a/r housing on a stock s5 hot side.)

 

Are you maxing out the AFM?

 

maybe the turbo is running out of breath? Wouldn't being in a higher gear produce a higher load on the engine and bring more air into the engine? So it might not be a problem in the lower gears but when the volume and pressure of the boost at the top of 4th and 5th gear increase to such a level the turbo can't keep up. Idk, just an idea, but I'm not exactly clear on what I'm trying to say. GL.

 

Motor boost fine when it's cold after it warms up. But once it fully heats up, that's when I the 6500rpm problems begins. I don't think the turbo is maxed out. I have the wastegate at 10 pounds and it holds 10 pounds even when I have the wall of no power. I'm getting stumped.

 

Also would having the silencer in, cause to much back pressure for it to stop spooling the turbo? I took my silencer out and DAMN... 15 pounds and leaned out nasty. I don't believe my tps is bad since I can read it from my safc.

I'm going to loosen up the wastegate, and see what happens. Hopefully it's just too much back pressure that cause the turbo not to spool in 4th or 5th. (But it doesn't make sense why it does it when it's hot.)

 

I was reading about back pressure, and how there is a ratio. I am going to see if I can find it. Maybe this is back pressure related? I had the silencer in when the 6500rpm problem happens in high gears.

 

I don't believe it's back pressure related, now. Can anyone tell me if the stock knock sensor really does anything useful? I am finally hitting a "wall" it just cuts out the ignition. and fuel leans out. Just for a blimp second like a fuel cut. It just bam stops making power. Then pulls hard again.

I am wondering if the having the knock sensor loose and not on the rotor housing effects it's signal to the ecu. I don't have a fuel cut on the ecu, since it's chipped. I am running 10 pounds and 11.2 afr all the way to 8k. It does this in 3rd gear at 6200 rpm now and up high gears as well.

 

I think it retards the timing a bit when the knock sensor senses something too harsh, which could also reduce boost. Not sure if that could cause this much of an issue though.

 

How is your ignition setup? what plugs/leads, Got a hks twinpower?
If you are indeed holding boost but ceise to make power could very well be due to spark blowing out...

I had this myself, no power above 5500 @ 14psi and the twinpower with b9egv plugs made the dIfference!
I now got the greddy re10 plugs which even feel a lot better then the b9egv's

 

I am running 1 msd 6a on the leading coil and trail plugs all around. I should look into getting the hks twin power. I've also heard that if the knock sensor is unplugged the timing is locked, for ignition. If that's true, I'm going to unplug it since, it's on the front iron. (I have s4 keg and don't feel like drilling and tapping below the oil fill neck.

 

Also today, I noticed the check engine light comes on when it hits the cut. It seriously feels like a boost cut. But wtf... Hmmm

 

lol, I cannot wait for it top stop raining. Since I am would feel really stupid. I think all of this problem may of been from the restrictive pill on the pressure line... I won't know until I get into 4th gear again.

Things done since then (Unplugged knock sensor so timing stays locked.)

 

There's a reason you have a knock sensor... and it's not the only thing that can result in retarded timing.

 

Well with the knock sensor plugged in and unplugged makes no difference. I have attached to the front iron, where one of the screws that hold the p/s and a/c bracket on. It's a pretty useless place, for it imo. But I can hook it up just to see if doesn't change.

I have my safc +35 from 4500rpm+ so I forget how much of the % is that I am retarding my igniting timing. Also there's some vibration that probably would cause the knock sensor to go crazy, I don't want it to retard the ignition timing to bad.

The other night I popped my hood after a hard run with cut, and my hot side was glowing red. So timing + too much fuel? Running 11.1-11.9 afr's to 8,000rpm. I checked codes was showing code 8 and 18, (afm and tps) I disconnected the battery to reset the codes and drove it around to see if I can have them come on again. So far all good, no cuts or anything. But it doesn't help it's snowing right now.

 

this is helpful, I am having a very similar problems myself now. I thought maybe my catyltic convertor was clogged so I cut off the stock y pipe and mufflers and hollowed out the cat, for now I'm running it open after the hollowed out cat. Anyways, it seems I hit a wall in acceleration at high rpm (6k rpm) but I have an FCD and my AFRs are 11.5 or so all the way up. My turbo still glows quite a bit, I still need to double check my ignition timing though. I'm gonna try and reset the computer first, thanks for the idea.