any turbo engine tuners out there today?

[vettestr]

I have a couple of questions about timing/ignition and amount of retard suggested for a turbo'd engine. I am only running 10 pounds max. boost so not on any ragged edge but would appreciate a little pointers and theory here.
If you have a few moments for a couple of questions I would sure like a sanity check. Please call me on my dime in the sates anyway 1 866 811 7461 or PM me with a number & time I can call you on.
355 inch Small block - wet or suck through turbo with waste gate set at 10 PSI. initial timing at 18 degrees and mechanical of 14 degrees available in at 2300 RPM. - static c/r is 8.4 - cam is a mild street cam not a turbo cam with 110 lobe separation - 224 int 231 ex @ .050 - 480 gross lift (just had to have a little lope on idle so I went with this as a trade off between ideal turbo cam and a rough idle. 3;55 rear gear supplied by a 6 speed tremec. Turbo was sized to engine by Turbonetics so it should be about right for the engine. THANKS AGAIN Jeff C

[hpbugeye]

try this site
http://www.theturboforums.com/smf/index.php

1 degree of retard per pound of boost
AF of 11 to 1 is safe for boost 14-1 with out boost

the LM1 by inovate is a must have for tuning a turbo set up. Don't ask how I know.

[vettestr]

Great site with a lot of info, Thank you

[enyawix]

initial timing at 18 is too much! I tune using my knock sensor. I would also use the stock cam shaft or the F303 cam.

[vettestr]

A little time has passed since original post and have made several changes already. This is the car as tested in the new issue of Kit Car Shoot Out titled Hot Rod Cobra. We took her to the test with about 20 miles on engine before rolling into the trailer headed to California. Without testing and trying to represent the average customer car or at least one non -turbo'd we turned the pop off down to 0 zip nada. This was a big mistake we only found after turning it back up and completing the tunning.

The system is wet or is a draw through turbo system. The pop off valve when opened returns fuel charge back under the carb but on top of the plate separating feed to the turbo or makes a big loop and kills the performance until the valve closes again. I bet we took 75 horsepower out of a maybe 290 HP engine when not on boost. Live and learn I guess.All the stuff in the intake diverting to turbo makes it run like it has a 1 barrel carb when not on boost !!!!!

The ignition/timing is a homemade system of MSD - 5 pin GM module - knock sensor controller and a pressure switch. We do run 18 degrees initial timing with another 16 degrees mechanical in by 2600 RPM for 34 total. If the Hobbs pressure switch sees 4 pounds of boost it grounds the 5 pin module that retards timing by 10 degrees and the knock sensor retards until no knock is present and turns on a red light so we no it is happening.

When no boost (10 PSI max) is present it runs on a max of 34 degrees and loves it. If boost comes on the knock sensor watches for issues and the Hobbs switch retards 10 degrees instantly so now only 24 degrees and it seems to work well without needing further retard from knock sensor. I am working on an alky injection to come on with boost but have not finished it as we are pretty busy. Great problem to have. jeff c

[enyawix]

18 degrees initial on what fuel?

[vettestr]

Originally Posted by enyawix

18 degrees initial on what fuel?

We are running 92 octane pump gas. I pulled a drum fuel monster out of this car to be able to run pump gas. The c/r is 8.2/1 with pretty much stock crate engine other than a cam change.

You seem shocked at 18 degrees but many are running locked distributors and int he 24 to 28 degree range from scanning all the turbo web sites. I have years of blown engine history and it would be common to run up to about 32 degrees with a fixed mag and no mechanical advance. I am learning boost is not just boost as the turbo are a different critter than my roots type blowers.

jeff C

[enyawix]

At 8.2/1 I can see that