Turbos and timing

[Humble]

This one is aimed at Wally and anyone else running efi and a turbo. What kind of timing/advance are you running and how much boost? I'll be hitting the dyno on Monday but right now my car doesn't want to wind up above 5k under load and I think it timing related. I'm getting about 15 psi boost pretty easily but it just hits a wall at 5k and I back out of it because I think I'm hearing detonation. I've got 34* by 3k off boost, and as soon as I get 3psi it backs off to 24* and down to 20* by 15psi. I'm not sure if thats going to far or not far enough. Free revving the engine has no problem and goes all the way up to 7500.

[JIMP]

Hello Humble

on a T1 turbo but carburated we made some tests and at 1.1bar boost it made it the best with 20o, we went through 18-26o and it liked better the 20, with the higher settings -even 26- not detonating but not helping the engine to rev fast through the rpms. If the whole setup of yours is handmade, please consider the following: I had a similar problem with a Golf G60 which I converted to turbo, as the piping and turbo sizing was made by me without any previous experience, I had a very similar problem in 5500 with the engine literally dropping in a hole without wanting to do anything until I backed off the gas pedal. Same as you free revving no problem, the cause was 1) to small turbo housing which in 5th gear and 5500 couldn't pass the gasses. I put a bigger one and oh! it was another car already. now the hole moved to about 6500 but hadn't any sense to enlarge it more because of the lag, so.. I adreesed my self to someone working with turbos for years and he started laghuing when he saw my setup. The problem after his guess was that I had a 180 turn in the turbine exit for the gases (with a very big radius though in my opinion like 4"). indeed this was the problem as I completely inverted the turbo so as the exit to come to the other side so as not forming a 180o turn and voila! every problem dissapeared in a magic way, letting me to thought that I could save the turbo housing that I changed, maybe it wasn't needed. That's all hope I help you for a little brainstorming..

Friendly

Dimitrios

[Wally]

I'am having trouble running higher than 15 psi as well. It revs easy through the rpm band all up to 7K, but anything more than 15psi and it knocks. The safeguard takes care of it, but its annoying anyways.
I run up to about 24 degrees up to 15 psi iirc, but need much more retard per psi after that, and even then it still pings but I am still experimenting at what retard it doesn't ping anymore. I now have water/meth injection and it helps a bit but not as much as I hoped.
My conclusion for MY set-up: my turbo/turbine is too small: it creates too much back pressure and also the compressor gets out of it effeciency area: at 1 bar its probably in its 70-75% efficiency zone, but above it gets probably to 60-65%, creating more heat when compressing air...

FWIW..