boost drop *only* in second gear??

[gwumpkus]

Hi folks, I'm experiencing a strange phenomenon, that the boost only gets up to 0.5 bar on second gear! First gear, it boosts to 1 bar seemingly without prob, but doesn't get beyond 0.5 at second. Any ideas? I've got an Aristo 2J in, with usdm turbos (550 injectors pending, due to suspect resistor pack).. Thanx for any advice folks

Michael

 

[mjsn1]

What type of transmission you have?
What about the other gears like third gear, because you cant know your boost in first gear.

 

[gwumpkus]

I have a 5 speed R154 transmission. Er you can't know boost in first great? Hmmmm perhaps what I meant was that the boost gauge would continue as the revs went up, hitting about 1 bar at 6500 rpm, but when shifted into second, it kinda doesn't go beyond 0.5 bar.. N third gear is similar to 1st,, goes continuously up as the RPMs went up.. doesn't sound normal, does it? My mechanic has swapped in another ecu with similar results... Weird no?

 

[mkiiichip]

It takes until 6500 RPM to reach full boost, on stock twins? That doesn't sound normal either....

Sounds to me you have more than just a second gear issue.

 

[te72]

It takes until 6500 RPM to reach full boost, on stock twins? That doesn't sound normal either....

Sounds to me you have more than just a second gear issue.

I agree, when I had the boost controller equipped to let me past 12-13psi, I would see 1 bar right around 3k. A gear specific boosting issue, that is an odd one... so, 1st and 3rd gear behave as they should, but 2nd you can't get more than .5 bar? I'm at a loss here. Your car throwing any codes or displaying any other odd behavior?

 

[525gte]

could be map sensor. Maybe the turbo is not buildimg enough load in 1st due to it being to short. And 2nd having longer gears allows the turbo to work harder. I'm not talking about boost levels but load on motor . Just ideas. Maybe boost leaks

 

[ifyouaint1sturlast]

Electronic boost controller?

 

[gwumpkus]

hmm..i'm suspecting some sensor as well. thanx for all the advice.. it may be useful to the shop as we investigate this crazy phenomenon.they've been investgating the fuel delivery system as well.... hopefully something turns up..its weird, that there doesnt seemt o be anythin else wrong...just this weird "boost cut"...!!

once again, thanx everyone, i'll keep all posted about the findings..

PS: i'm not using an electronic boost controller, the entire setup is pretty much stock.. but damned..u get 1 bar at 3000 rpm??.. imma get me one of those!!..hehhe..

 

[ifyouaint1sturlast]

Good luck!

 

[te72]

...but damned..u get 1 bar at 3000 rpm??.. imma get me one of those!!..hehhe..

It's not just the boost controller. The way my head is ported makes it a mid range monster. As a side effect, the stock twins completely choke the engine around 4800rpm. Having an engine that plateaus in power delivery "feel", that revs all the way to 7200? It's an odd feeling.

 

[ifyouaint1sturlast]

It's not just the boost controller. The way my head is ported makes it a mid range monster. As a side effect, the stock twins completely choke the engine around 4800rpm. Having an engine that plateaus in power delivery "feel", that revs all the way to 7200? It's an odd feeling.

Curious, what does it feel like when it "chokes" the engine? Just.. unpowerful? Or hard to climb the RPMs?

 

[te72]

Starting at cruising speeds around 2000rpm, starts spooling around 2500, peak boost around 2800-3000, pulls HARD until about 4800-5000, then just feels like you're pressing the gas just to make more noise. The power "increase" if you will, plateaus at that point. Dyno proves that it still makes more power the further it revs, it just doesn't feel like it once you hit the 5k mark.

Definitely looking forward to fitting the new turbo at some point to compare the feeling.