casey007

Hello

I purchased a used STS twin turbo kit off a forum member recently, the kit came with 63 precision turbos and a manual boost controller. The tuning has been through STS and applied with my Predator tuner. I had planned on running 8 lb of boost.
The issue I am having is the max boost I can achieve is 5 lbs. I have checked for possible leaks and couldn't find any. An area of a bit of confusion on my part is the lines to the wastegates. My understanding from the manual was to hook up a 1/4" id line to both the wastegate bottom ports and return to the manual boost controller then to the brake booster. The top port on both wastegates wasn't connected.

STS told me to run another line to the top ports on the waste gates and run to the brake booster. I still can't increase my boost and don't know what to do next.

My wideband isn't hooked up yet and using the Predator real time data.
At boost the oxygen sensors read .9500 to .9800 milivolts, manifold absolute pressure is 14.7, maff sensor mass air flow 361.6. STS tells me the oxygen sensors should be .900-.920. I enriched by 5% and it ran like sh_t, then brought back down.

Your help is appreciated.

brandtdavis

Here is a link to my recent DIY STS build w/o boost controller. I don't have a good picture of the wastegate (only 1 in my kit) but you should have the vacuum line to the top side. Look on Page 7 and 40 of your manual you will see. The side you can see from the back of the car is vented to atmosphere. What if you take the manual boost controller out of the system first and see what you get. If you want to chat in person PM me your number and I will give you a call or take better pics if you need it.

http://forums.corvetteforum.com/c5-f...diy-build.html

user_name

I can't be of too much help with your boost issue, but I will warn you about your tuning method. You need a wideband and a knowledgeable person with hpt or efi live to tune a boosted car like these. I'd say that same person might be able to get it done with a Predator, but it would be kinda like doing it with 1 hand tied behind your back. You are heading for a blown engine.

casey007

Thanks for your advice and I'll take it. I have been leary about there tune especially when I have now received three and stilll issues are present and they tell me to tune it in with my predator. I would have been better off first taking the car to a shop with a dyno than paying them $300.

brandtdavis

I got your email, let me know if you did not get my response.