Overboost in sw20

FXGTV · Post by **FXGTV** » Tue Dec 18, 2007 5:19 pm

I have overboost problems in my sw20 (yay). The previous owners installed a turbosmart bleedtap style boost controller but this is very limited and makes it hard to know exactly where you are in terms of boost levels
My question is, can i fix this problem by buying an electronic boost controller with a good reputation...or is it a bit more involved than that?

AJz · Post by **AJz** » Tue Dec 18, 2007 5:32 pm

hard to tell aye, has he could have left the factory one in aswell. That doesnt always end well. usually you find the cut out real quick

All manual types dont have any easy way of setting a correct level of boost. You just have to play around. My gt4 i previously had did not like having a bleed tap on it. Would sometimes cut out on a cold night from spiking too high.

Electronic ones need to have quite a bit spent on them. HKS and Profec B boost controllers seem to be the best bet. Afaik though, your still setting a gain level not "dialing in" the boost you want. Feel free to correct me if im wrong.

What boost is it running and what does it spike to ??

if its an early mr2 they cut out about 14-15psi from memory

Boosted_162 · Post by **Boosted_162** » Tue Dec 18, 2007 5:36 pm

I had a profec b spec 2 in my GT4. Was sweet, no problems. Hit boost cut on cold nights, but i ran right at my cut. Plus it probably wasnt set right.

FXGTV · Post by **FXGTV** » Tue Dec 18, 2007 6:03 pm

Well the thing is a dont know what boost it is running as i've only got the standard boost gauge to look at. The previous owner told me boost cut was at 16 (its a '92). There is a boost spike thats annoying me too, as at times I have next to nothing from 5500-7000.
I'm not racing it or anything, but i'd like to think I have a smooth turbo power band all the way through the revs.

This is my first turbo car so its hard to know what to look for.

mr2_t · Post by **mr2_t** » Tue Dec 18, 2007 7:35 pm

CT26 turbos (on the Gen1 and Gen2 SW20's) top out at around 5500rpm. Running more boost isn't going to change this unfortunately.

I've got a turbosmart gated bleed valve - might be the same as yours, with a ratcheted adjustment. Its set to 15 PSI (good for 160rwkw) and doesn't spike noticeably. Dialing it in is pretty much a matter of winding it open incrementally until you get to the boost level you want, very unscientific but it worked for me. As mentioned above it would pay to check that the valve has been installed properly , if the factory boost control (TVSV) is still connected you will get unpredictable results...

To start with though I'd recommend you get an aftermarket boost gauge of some sort - they aren't expensive and easy enough to fit. The factory gauge is a bit useless really.

Also - i reckon an EBC is a waste of money on a gen1/2 sw20. The main reason people buy these cars is bang for buck, you could easily spend a 1/4 of the car's value on an EBC. Keep the bleed valve!

HTH

AJz · Post by **AJz** » Wed Dec 19, 2007 12:03 am

yea agree, ct26's top out about there, thats normal dude.

Akane · Post by **Akane** » Wed Dec 19, 2007 8:50 am

I have a Turbosmart turn knob thingee, their cheapest boost valve, no complain at all, boost fine no spike holds steady. So I doubt it's the actual product.

But then again I don't have the CT26.

When I had the CT26 I also had a homemade bleed valve, no matter how much i dail the boost will drop after 5000rpm, but it does drop in proportion to how much you dial.

Heylin · Post by **Heylin** » Wed Dec 19, 2007 3:04 pm

I run a GFB Atomic which uses a needle \ grainger valve setup, I am running a CT20b at 15PSI and its very rock solid at max rpm, no spiking whatsoever.

Skin · Post by **Skin** » Wed Dec 19, 2007 3:55 pm

Fix all your problems and buy my ct20b!!!! :lol:

Al · Post by Al » Wed Dec 19, 2007 3:55 pm

Get a boost gauge to start with.

Disable the T/VSV. Theres two pipes that come out of the actuator on the turbo. One will have the bleed valve on it, the other one will head south somewhere that you can't see. Cut that pipe and plug it up with a bolt and cable tie. Problem should be solved.

If you want more boost than the boost cut will give, find the boost pressure sensor on the drivers side rear of the engine bay. It will have an electrical connector on the passenger side, and a hose going into the base. Pull the hose out of the base and plug that up as well. No more boost cut.

ChaosAD · Post by **ChaosAD** » Wed Dec 19, 2007 6:51 pm

See if it does it with a pipe straight from the compressor housing to the actuator. If it still does it then, no ebc will fix it. You would need to remove the turbo and port the wastegate

touge rolla · Post by **touge rolla** » Wed Dec 19, 2007 8:00 pm

what Al said,
and chuck a Gizzmo IBC in, cheap reliable electronic control with four different boost settings to suit your mood/opponent/fuel usage

MR2SIK · Post by **MR2SIK** » Wed Dec 19, 2007 10:15 pm

i really dont see the point in multi step boost controllers, Set it to one and use your right foot to control for anything lower :lol:

(although im suffering from underboost problems at the moment :lol:

)
factory 10psi blows :evil:

FXGTV · Post by **FXGTV** » Thu Dec 20, 2007 2:59 pm

Wow, thanks guys. Its good to know the drop off at 5500 is normal

I was a bit worried there for a second :twisted:

Heylin · Post by **Heylin** » Fri Dec 21, 2007 12:01 pm

i really dont see the point in multi step boost controllers

True, youre only running full boost for a short time so the fuel consumption theory is out, and really you only want to run as much boost as you can reliably.

I wouldnt feel comfortable running my CT20b anywhere over 15PSI on the stock engine with higher kms.

FXGTV · Post by **FXGTV** » Fri Dec 21, 2007 5:35 pm

Heylin wrote:
i really dont see the point in multi step boost controllers

True, youre only running full boost for a short time so the fuel consumption theory is out, and really you only want to run as much boost as you can reliably.

I wouldnt feel comfortable running my CT20b anywhere over 15PSI on the stock engine with higher kms.

And thats what i am going for, reliability. Last thing I want is to join the 3S blown engine club

OMG so shiny! · Post by **Dell'Orto** » Fri Dec 21, 2007 5:52 pm

Heylin wrote:
i really dont see the point in multi step boost controllers

True, youre only running full boost for a short time so the fuel consumption theory is out, and really you only want to run as much boost as you can reliably.

I wouldnt feel comfortable running my CT20b anywhere over 15PSI on the stock engine with higher kms.

23psi is ok in short bursts :lol:

MR2SIK · Post by **MR2SIK** » Sun Dec 23, 2007 6:21 pm

FXGTV wrote:

And thats what i am going for, reliability. Last thing I want is to join the 3S blown engine club

Its only a matter of when... not if :lol:

touge rolla · Post by **touge rolla** » Sun Dec 23, 2007 10:25 pm

Heylin wrote:
i really dont see the point in multi step boost controllers

True, youre only running full boost for a short time so the fuel consumption theory is out, and really you only want to run as much boost as you can reliably.

I suffer from an inability to not floor it :lol:

so to save fuel it is good to be able to drive around on 6-7psi maximum
plus i don't want or need 1 bar all the time, so like to drive around on just standard boost and only turn it up when i feel the need. (e.g overtaking or letting a gtst driver know they aren't THAT fast :wink:

)
Everyones different i guess, and i feel the need to play with my boost setting whilst driving

Al · Post by Al » Tue Dec 25, 2007 11:03 pm

touge rolla wrote:so like to drive around on just standard boost and only turn it up when i feel the need. (e.g overtaking or letting a gtst driver know they aren't fast AT ALL )

Edited for truth.