Boost problems at high rpms

[lynx]

Hi

I have some very weird problem.

Setup:

k26/t04e
green injectors
adu ex. mainfold
bigger intercooler
etc,

Problem is: it peaks just so much I turn wastegate. Example . . . max boost is ca. 2bar . . . but at the redline it drops to 1,4. Even if i turn wastegate back and turbo peaks to 1,7 . . . it drops still to 1,4 no matter witch gear.

I think it' s not any boost leak, because @ 2bar and 4gear it hold nice pressure before it begins to drop. And 90% of pipes are new, because of new interooler.

I' ll tried even to disconnect n75 from turbo . . . still drops to 1,4. Tried new wastegate spring, still the same.

Last year there wasn' t that problem . . . it was holding a pressure to redline just fine. Car runnig normal, feels good, but the top end was better before.

I' ll remember just one day when car was going better than ever @ the top end, but that was just one day.

There's no any codes in ECU, a/f gauge shows rich . . . I' m running out if ideas.

I' d tried to search at the forum, some problems was alike, but . . . not exactly the same.

anyone?

[kwlw]

Hi
Problem is: it peaks just so much I turn wastegate. Example . . . max boost is ca. 2bar . . . but at the redline it drops to 1,4. Even if i turn wastegate back and turbo peaks to 1,7 . . . it drops still to 1,4 no matter witch gear.

Sounds like turbo is not able to supply enough air for the engine at high rpm's. This can be due to two reasons. First is turbo itself somehow is not able to hold pressure at high flow, second is that engine is not able to supply enough exaust gases to make turbo spool to make enough flow.

Not sure if this helps, but in your place I've also check fuel pump debit/flow under pressure.

BTW: Have you done any changes to the intake tract like cams, intercooler, etc. ?

Sau

[lynx]

Sounds like turbo is not able to supply enough air for the engine at high rpm's. This can be due to two reasons. First is turbo itself somehow is not able to hold pressure at high flow, second is that engine is not able to supply enough exaust gases to make turbo spool to make enough flow.

Not sure if this helps, but in your place I've also check fuel pump debit/flow under pressure.

BTW: Have you done any changes to the intake tract like cams, intercooler, etc. ?

Sau

Last year Turbo was able to hold pressure till redline. But if I think back, last year I had original cams, now I have 7A ex. cam (ecu progammed for that). I can' t remember what happened last year if I replaced ex. cam . . . at the witer car was not running approx. 4 month . . . I really don' t remember. But 100% sure, that last summer I was able to see @redline ca. 1,8-1,9bar overboost.

I have new intake track from turbo to original pipe witch goest to inlet mainfold, and 600*300*76mm cooler.

About fuel pump . . . yes . . . I have to check it. But what else?

[AAH!]

If you have had the ecu remapped for the new 7a cams maybe it was mapped for the boost to drop off as the revs reach the red line. I believe it is good/normal practice for a car to be mapped this way...for the protection of the engine.

[Greg_S]

totally agree angus, mine has been mapped to drop boost off towards the redline & also to ensure the turbo is not over spun

[lynx]

If you have had the ecu remapped for the new 7a cams maybe it was mapped for the boost to drop off as the revs reach the red line. I believe it is good/normal practice for a car to be mapped this way...for the protection of the engine.

agree, but could ECU still manage to boost, if n75 hose from turbo has been disconnected?

If I look turbo map, then it could be more boost at redline.

I got more boost even with chip wich are mean to be stock hardware (I bought car with it). Last summer (I have videos, that why I know it ) with that software was no problem with boost.

Let' s say that everything is normal etc. But I talked before that one day when car was going best than ever, and that was just normal day like any other (whether was ok, etc).

[lynx]

problem solved . . . at least this one.

I' ll tried all-most everything, but still no . . .

Last thing on my mind was cams . . . I use original 3B inlet and 7A out. Just to be sure that everything is ok, I checked cams too. And what did I see? Inlet cam was a tooth wrong . . . it was a one tooth later than it should be.

Ok, with friend we put marks right, like they should be and that problem sovled. Now it holds pressure just fine, but . . . at the middle rpms there' s certainly less torque and maybe that' s why I feel that car is slower than before. But I feel that car is slower now, what can I do . . . It' s really hard to say, if the higher rpms are now better (even with more boost).

Anyway . . . I think that' s it . . .

P.S> I can' t help if I repeat myself . . . before that, I liked car more . . . even if that' s was a right setup!