My turbo dosent hit full boost until 6000 rpm???

[hippy]

Yap thats right it s a 98 gsx with a jdm 6 bolt my mods are t3/t4 scm61 turbo ported, 2 1/2" intercooler piping,29 x12x3 fmic, hks bov, 3" gm maf and translatour, 680 injectors , 255 pump, dsm link v2 car was on the dyno and all tuned on saturday but the car wont make full boost untill 6000 rpm it is only hitting 13 to 24 psi i have a greddy profec spec 2 and we can not get it to go any higher so im goin to get a mbc and put it on and crank it up soem more. Im wondering if the greddy profec is making it slower to spool up?? Also have a 2g manifold with 3" exhaust and a tial wastegate! What can i do to get my boost higher and quicker?? Thanks!

 

[CanadianTSi]

You either have a big boost leak or and exhaust leak pre turbo.

 

[dalatinromeo]

Def check for a boost leak.

 

[nicknorth11]

I don't know how much this will help, but a good friend of mine has a similar setup with the same turbo with no boost leak and he doesn't hit full boost until he is around 5200-5300 rpm. So, you may indeed have a boost leak, but I wouldn't expect too much better spool up time. That turbo is just too big to spool quickly on our cars.

 

[daren_p]

Check for boost leak & exhaust leak first. Have you tested the Tial WG to make sure its operating properly? For the Greddy profec, the amount you can turn it up is a multiplication factor of the base wastegate pressure. Not sure the exact multiplication factor but say it was 2x, that means if your tial is set at 12 psi, the profec will only be able to increase the boost to 24 psi. I believe the multiplication factor is actually higher then 2x though...

I have the Profec type S, my base WG pressure is set at 12 psi. Origionally I couldn't see over 18psi with the high setting on max because it had an issue in the software. They upgraded the software & now I can run 20 psi and the high knob is just over half way up. As far as I know this was only an issue with the Profec Type S but you may want to contact Greddy to make sure.

 

[crunchymilk]

Definitely sounds like a huge exhaust leak. Check the head/manifold and the manifold/turbo for leaks. You're likely to find black carbon build up there somewhere.

 

[hippy]

Im pretty sure i dont have a boost intercooler leak ill dbl check!! ALso the turbine housing that comes of the turbo to the d/p is allways coming loose on me but it was tight on the dyno so i know that wasnt it for a fact!!!

 

[Grn95GST]

I am with everyone else. You definitely have a leak somewhere. I get full boost ~20psi on the scm61 at roughly 4400-4600rpm in 3rd gear.

 

[hippy]

Ok last night i did a leak down test in teh intercooler pipes and not one leak as i suspected i used all the t bolt clamps and tighten them very very tightly I have a 4" forced performance intake as well with a 4" kn filter man i wish i could get this to spool up quicker?? No exhaust leaks either! What could be doin this???

 

[nicknorth11]

do you have a big 02 housing to go along with the 3" exhaust? i can't think of anything else that it could be.

maybes:

boost leak
weak link in exhaust (too small of an 02 housing or still have cats in)

I'm telling you though, it's honestly not supposed to be too much better than that. Does it not hit 24 psi until 6000 rpm? my friend wasn't hitting 17psi until 5200-5300 rpm, so that sounds about right. you just picked a turbo that is notorious for S-L-O-W spool up on our cars. (if you ever consider a new turbo, think about dual ball bearing if you want better spool and high hp). sorry if this doesn't really help, but it's the only advice i have. good luck.

 

[blackifre22]

do as everyone says check for leaks then look at your tune. if you have low timing and running rich it will also effect your spool times ect.

 

[Coup D E'Tat]

I'm telling you though, it's honestly not supposed to be too much better than that. Does it not hit 24 psi until 6000 rpm? my friend wasn't hitting 17psi until 5200-5300 rpm, so that sounds about right.

Do not post misinformation.

My friend's SC61 hits 20PSI around 4500RPM in third, on a stock 7.8:1 6-bolt, FP2 cams, and a JMF SMIM. I've only made one 1-2-3 pass on mine, so I can't give spool times, but I can tell you it'll build full boost well before 5300 running properly (I found boost leaks later that night.)

 

[scheides]

What do you have the base timing set to? If the timing is turned way back, it may cause this.

 

[Ultimatedsm]

Bypass your Boost controller and see if it builds boost slowly. Or borrow someones MBC for now and see if that made any kind of difference. I had a BAD MBC and it gave me terrible lag inbetween shifts.

 

[hippy]

I have no leaks in my int my intercooler pipes and i have a 4" forced performance intake with 4" kn filter what can i do to make it boost up quicker?? WHat if i go to a mbc instead of the greddy ebc?? I really think its holding the boost back for some reason.
And its 14psi not 24 psi i wrote at the top!!

 

[Coup D E'Tat]

How do you have the vac lines ran to the wastegate?

 

[1SloColt]

Wow, I was in the same boat as you once when I first bolted on my sc61 to my bonestock 90 longblock. I did some fuel compensations beforehand and had the boost set to around 18psi or so. Unfortunately the turbo didn't spool until about 5500rpm, and the car went no where. So first thing i did is what everyone on here is suggesting, boost leak testing, check for exhaust manifold leaks. Mine were perfectly sealed, as yours is. So I figured it had to be the tune. Boy was I right. Car immediately went from 5500 spool and no power to 4500 spool and nasty power. After some more fine tuning I now hit 20psi at 4250rpm, with a larger exhaust turbine housing and turbine wheel than you are running. Is your turbo internally gated? That could also be a problem. Try tuning first, then if that doesn't help at all look for the flapper to be blowing open, if its internally gated that is. My car seriously felt like it was running a N/A 4g63 when i first bolted it on, and by the end of 10min with some tuning it felt nasty.

 

[hippy]

Ya well i had it all tuned on the weekend hat in my tune could i change to make it spool up quicker?? My timing some one said?? Thansk guys!

 

[nicknorth11]

Quote:
Originally Posted by nicknorth11
I'm telling you though, it's honestly not supposed to be too much better than that. Does it not hit 24 psi until 6000 rpm? my friend wasn't hitting 17psi until 5200-5300 rpm, so that sounds about right.


Do not post misinformation.

My friend's SC61 hits 20PSI around 4500RPM in third, on a stock 7.8:1 6-bolt, FP2 cams, and a JMF SMIM. I've only made one 1-2-3 pass on mine, so I can't give spool times, but I can tell you it'll build full boost well before 5300 running properly (I found boost leaks later that night.)


Just because you saw a different situation doesn't mean I posted "misinformation". I don't know how much the cams help your friend's spool up time, but I know for a fact my friend's car doesn't hit 17 until 5200-5300. (with NO boost leaks and tuned by one of the most reputable tuners in town).

 

[1SloColt]

If an sc61 with a .63 t3 housing isn't reaching full boost, lets say 20psi, on a bone stock 90 4g63t longblock by 4500rpm then something is wrong. If the car has cams or intake manifold or more sophisticated bolt ons, the spoolup time should change minimally. A 7.5:1 compression built 6 bolt with a .58 t4 housing sc61(or pt61) with 272s, SMIM, large intercooler piping and intercooler will reach 20psi at 4600-4800rpms with a decent tune. I have quite a bit of experience with the turbine housings/wheels that can be attached to the gt40 compressor. Of all the gt40 compressor turbos I've seen on 4g63s, none have reached full boost, which could be upwards of 30psi, after 4800rpms. These turbos range from bolt on scm housings to .68 t4 housings. Point being, either your buddies tach is wrong, or his boost controlling system is wrong, or something is wrong with the setup. Because a t3 sc61 should not hit 20psi anywhere close to 5300rpms with a good tune.

 

[Coup D E'Tat]

I don't know how much the cams help your friend's spool up time, but I know for a fact my friend's car doesn't hit 17 until 5200-5300. (with NO boost leaks and tuned by one of the most reputable tuners in town).

I don't care if Jesus, Mohammed, and Moses tuned the guy's car. Either the tune isn't right, or the car has mechanical problems.


Edit : By the way, the guy up a few posts spooled his SCM61 by ~4500 on stock head/block.

 

[hippy]

All i know is i want it to spool up quicker im goin to try a mbc on today and see if taht makes any difference i hope it does!!!

 

[Coup D E'Tat]

How do you have the vac lines ran to the wastegate?

....

 

[hippy]

Ok i unhooked both vacume lines of my wastegate and it only goes to about 10 psi at 6500 rpms this really sucks i wanted to race at our sport compact this weekend! ANy ideas wha ti should do next?? Does it sound like the wastegate?? Thanks guys!

 

[DSMcrazy3]

I had the same problem when I first boosted, for me it turned out the bottoms of the rings for the exhaust manifold gasket had been burned away, so the air was escaping there before the turbo..You're sure that isn't it though? Pulled the manifold off to look?