Boost problem after 5000rpm on a rebuild non sequential 13brew
 

Hi guys... i bought a 95 JDM Rx7 with a rebuild engine. The guy who did the rebuild converted it to non sequential! So far the car has got an apexi intake / Catback as bolt ons! Cat isnt in the best possible condition i think as i hear a rattling noise from down there...anyways.. i ran the engine in as i should... well so my problem it starts boosting from 4000 rpm and as i pass 5000 rpm the boostgauge starts jumping from 0.7-0.4 up and down and the rpm rise very slow... it feels like it gets no fuel... (maybe fuelcut?) i get a huge loss of power... what could be wrong :( thought about boost spike and therefore running into stock fuelcut which is like 0.77bar at 5500 rpm?! Ive got an electrical gauge from autogauge and i dont know how accurate and how fast it can react to even show boost spike?! ... what do you guys think?

Yeah, that does sound like fuel cut. Probably what you should look into next is a PowerFC, the car really needs a proper ECU to run well.

Dale

thats no prob as i plan to go for a decat and a downpipe and im gonna need it anyways ... just wanna be sure that its just the fuel cut so that i can keep going with my project :) without having to think of anything else!

So porting the wastegate should let that kind of boost spike dissapear right?!

Installed a restrictor plate today tried 2.5" first no change! Then even tried 2" installed it right after the cat. car became a lot slower but as soon as it passes 5000 rpm you just hear a wooshing sound like the sound of those huge trucks when they hit the breaks (engine break)? what ever... or the sound of an airplane taking off ^^...but no more power... like a valve is opening and letting all the boost out but the boost gauge still shakes and shows over 0.4 bar!? so i guess its not boost spike issues im having... but WHAT ELSE COULD IT BE :( ... im really pissed... just got the car and cant have at least a little fun with it :( ... didnt buy a 300 hp car to be driving arround with like 150 hp... pleeeease help me :( ... could it be a failing charge relief valve? Why do i need it anyways when im running parallel mode?!

check your intake piping for leaks

No :( checked... no leaks :( still does the same thing! :( :( :( could it be some kind of valve failing and opening after 0.5 bar?!"

I had a similar wooshing sound after 5k turned out that the reference line going to the BOV was pinched so the boost was opening the valve. Take the small line going to your BOV off while the car is running and see if there is vacuum. If there is then I would suggest doing the intake pressure test. The amount of small leaks I found was insane (Thanks Arghx) you can buy a tester or make one.

Good Luck
Mike

Is the CRV still connected in your non-sequential setup?

could it be the fuelpump failing over 50ß0 rpm and boost ?!

If you are hearing a loud "whoosh" sound, I doubt the fuel pump is your problem. But anything is possible at this point unless you have checked and eliminated what is not the problem.

pressure test

Thanks for the replies guys... swapped CRV with a second bOV and hooked it up as a BOV... so no more CRV and also the BOV vacuumpipe is ok :( ... mhhh will try a leakcheck tomorrow :(

For your old CRV location/new BOV, where is your vacuum source coming from?

took it right from the intake :( ... plugged the old one!

As a test to eliminate your boost being possibly being vented at 5000 rpms, you can remove them and plug the y-pipe nipples. Then you can see if you have boost beyond 5000 rpms. If you do, it's something wrong in your BOV routing. If you don't, then you still have an issue somewhere else.

ok just removed the BOVs and tried it... still the same... no power after about 5k in second ... didnt try the other gears as theres no point ^^... so no BOV leaking :( ... cant think of any other boost leak letting the car loose so much power to be honest :( will try a leaktest 2morrow ... but im not really believing that it will reveal anything :/

btw. when i took my foot off the pedal after 5k rpm i still heard a bOv kinda sound ^^ even though theres no BOV... thats normal right? or is there any other valve hidden somewhere ^^

^^^ Follow that advice

The sound you heard was compressor surge. The air still goes somewhere so it forces it's way past the turbo

I've heard a few cases of compressor surge, and I've never heard it sound like a "whoosh". You usually get the fluttering sound since the blades are still spinning.

its more like a whooo sound ^^ without the sh ^^... damn i cant get no rest untill its fixed :( ... but why the hell would a boostleak

1. not affect idle
2. not affect vacuum
3. just occure over about 5000 rpm while flooring it... or even with 90% throttle it does that... and loosing so much power... wouldnt it loose like max boost but still keep pulling even though it reaches only 0.5 bar!? :( ...

double post

I will take a stab at this.

1 if it is just a boost leak it will only leak under boost. Say it is a coupler that has a small split in it, under vacuum the split stays sealed, as soon as you hit a certain amount of pressure (.5 bar) the split opens and dumps the boost

2 same reason as answer 1

3 it would only show up when you are making boost which is in the 5000 rpm area (depending on how hard you are pushing it) if you stay light on the throttle you will not be making much if any boost.


Honestly do the pressure test it will be a definitive answer to a boost leak. When you do the pressure test keep in mind that the system will not hold the pressure for very long. Get a squirt bottle with some dish soap and water pressurize the system and listen for leaks, when you think you have found one spray the soapy solution on it and see if it bubbles. Check every vacuum line, every coupler, hell spray the solution on everything and see if there are bubbles.

Good Luck

Mike

Have you checked for ECU codes?

ok did a pressure test today... found a couple of leaks ^^... now i get boost even earlier... and the car cuts out even before 5000 rpm :D ^^... still the same problem... so no more leaks! checked my boost gauge (electronic type from Autogauge) ... took out the vacuum hose and it showed -0.1 bar :/ ... so i thought it might be off a little bit! took my bros boost gauge (mechanical type) and under full load just before it cuts out it shows 0.8 bar and then there is the huge loss of power ^^ and at the same time the pressure drops... sooooo ... could it be actually really be fuelcut as we mentioned it in the beginning? I think the stock ECUs fuelcut is at 0.77 bar after 5000 rpm! so thats my guess!?

BTW i dont run a ebc or mbc so could an electronic boost controller solve this or is it a wastegate issue?! ...

Thanks guys!