# turbo spool question. what are possible causes of slow spool?



## elRey (May 15, 2001)

turbo spool question. what are possible causes of slow spool after the obvious?

2.0L 16v 
stock CR (10.4-10.8:1)
E85 with advanced timing
t3/t4 .63 hot, 58mm cold inducer
internal WG
3" dp hiflo cat -> stock cat back
stock intake mani

Barring boost leaks, WG control issues, what other things could cause slow boost build?

My solenoid is pegged at 98% duty right until target boost is reached. With that said, the rate at which the boost is building kind of slows down as it approached target (16psi) EVEN thought solenoid is still at 98%. I don't have to worry about a spike because of this (not necessarily a good thing).

I have a restrictor in the source boost line between turbo and solenoid and the valve itself has a restrictor. I REALLY don't think is a boost controller/solenoid issue.

Could my 3" dp/cat into a stock cat-back make a big difference in spool up top?

I'll post logs/graphs later, but with target boost set @ 16psi I see 12psi by 4400RPM and 16psi not until 5500-5600RPM. If a didn't have the rate slow down I would probably see the 16psi by 5000-5200.

Thanks,
Rey


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## BoostedDubVR6T420 (Dec 4, 2009)

Boost leaks? Are you sure you wastegate is completely closed and is actuating properly?


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## boopizi (Dec 1, 2008)

I have been haven an almost exact issue. I'm running a evo III 16g however. It sucks. Iv been scratching my head raw. I don't see 5 psi till 3200. 15psi at 4200. And my full 22 isn't until 5k. I just replaced my turbo this week thinking for sure that was the issue... 

I however seem to have a small leak around my t.b. But cant seem to find exactly where. And even so it's barley noticeable. My buddy has an evo 9. He sees 20psi @ 3400. It makes me wanna cry. However I have not checked my waistgate since it has actully been installed. Lol. Iv been seeing Laggy boost for over a year now. 

Good luck. And would like to hear more oppinones? Maybe I have that poor of a megasquirt tune that my turbo can't physically spool up that fast? I didn't think I was running that rich...


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## BoostedDubVR6T420 (Dec 4, 2009)

Yeah if your running a 16g and you are not seeing boost till that late, you should return it right away to the DSM guy who sold it to you because its probably full of RTV.:laugh:


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## zwogti (Jan 11, 2004)

I will say a combination of a .63 back house, with the small stock cat back, what size xhaus do you have? 1.5 pipe?  2.5 pipe will help on the spool up and a small back house on that turbo if you want it to spool around 2-3K RPM. external wastegate work better.


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## elRey (May 15, 2001)

Stock MK4 cat-back = 55mm. And I expected the spool to start where it does. It's the slowing down of the spool as it approaches full boost that disturbs me.


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## [email protected] (Oct 6, 2009)

elRey said:


> Stock MK4 cat-back = 55mm. And I expected the spool to start where it does. It's the slowing down of the spool as it approaches full boost that disturbs me.


check for leaks. check to make sure the vband on the hotside/center section is tight and not cracked (common problem i found). Check and make sure wastegate is actually closed fully. I know on my big16g 22psi by 3500 was the norm. Also that stock catback is also killing you. A good 2~300rpms to be had there (from experience).


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## boopizi (Dec 1, 2008)

I know the turbo is good. I wasn't sure about the last one because it was a low milage used. I bought a rebulet one off of Blouch turbo, who is vary well respected in the evo community. I thought for sure that was the problem... I will pull my downpipie out this week. I wish I could see 22psi at 3500. Glad to hear someone has done so.


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## zwogti (Jan 11, 2004)

disconnect the catback xhaust from down pipe and go test it, see if it will spool better, wastegate or boost control also could be the problem.


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## elRey (May 15, 2001)

update: stock exhaust was the culprit. I install a 3" cutout right after the 3" hiflo cat.
close = same spool as before
open = totally different beast.


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## huichox4 (Nov 8, 2004)

elRey said:


> update: stock exhuast was the culprit. I install a 3" cutout right after the 3" hiflo cat.
> close = same spool as before
> open = totally different beast.


so at what rpm were you seen boost now?? 


by any chance have you posted your build in a Guatemalan VW forum?


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## elRey (May 15, 2001)

huichox4 said:


> so at what rpm were you seen boost now??
> 
> 
> by any chance have you posted your build in a Guatemalan VW forum?


I have some open/closed comparison logs I'll post. Tho they were NOT all out because then I realized my closed cutout boost control settings were not working for the open cutout . 

And someone else copied/pasted my build info there. Not me.


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## elRey (May 15, 2001)

here are some logs. I think it's obvious which are open and which are closed.


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## crzygreek (Jul 8, 2005)

Baring those other possibilities, your stock catback is causing a major restriction for exhaust gas flow. It is probably backing up all the way to the turbine and slowing it's speed by "capping" the maximum amount of exhaust gases that can spin it.

Get a 3" catback:thumbup:

EDIT: Just realized the date of the original post, i'm glad that it was in fact the issue and it is now resolved:thumbup:


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## elRey (May 15, 2001)

crzygreek said:


> Baring those other possibilities, your stock catback is causing a major restriction for exhaust gas flow. It is probably backing up all the way to the turbine and slowing it's speed by "capping" the maximum amount of exhaust gases that can spin it.
> 
> Get a 3" catback:thumbup:
> 
> EDIT: Just realized the date of the original post, i'm glad that it was in fact the issue and it is now resolved:thumbup:



Done. 











Graph right above your post is with this open/closed.


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## elRey (May 15, 2001)

Dare I say... I like the slow spool better. :screwy:

Now I hit peak boost of 20psi @ 4300 and hold until I usually let off @ ~5800.
Now I feel the rush to 4300 then it feels like a plateau. The rush feels more fun than the holding 20psi.

With the boost slowly, but constantly, rising to 20psi @ 5800 the rush lasts the whole run. True the rush isn't as brutal but it feels like the car has limitless power. All you need to do to tap into it is hold the throttle down longer.


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