delayed boost onset

[Alan L]

Have to ask the brains trust again. I suspect I know the answer, but hoping there may be other possibilities.
First track run after top end re assembly. The boost onset is a 1000 rpm later than normal - coming in gradually from around 4500 rpm. Hopeless.
Possible causes?
Thanks
Alan

[Tippy]

Here's what have led to slow response for me:

1. Boost leak
2. Retarded timing
3. Too rich or too lean mixture

[Alan L]

My timing hasn't changed - but my AFrs were rich. First run with the tweeked 007 fuel head. And at 3000' altitude when my previous tuning is at sea level. I will check for leaks - but it sounds like I may have tweeked too much extra fuel into the fuel head.
Thanks
Alan

[gsxrken]

A modified 3LDZ could be a lot of things but are you sure you need all the extra fuel? Maybe should step up to a larger snail and use the extra fuel instead of dialing it all out.

[Alan L]

I needed some xtra fuel after porting the heads and switching cams. Running out at 5500rpm.
So had the fuel head modded via Brian. This was the first run since. But the combination of 3000'alt and the xtra fuel flow in the head may have been too much. It is possible I tweeked the head too far. Apparently strange things happen when you try and max them out.
Back to square one. I can't change my turbo (race regs) altho I possibly could go to a K27 (930S). But I will wait til this turbo expires - enough things to concentrate on /resolve at the moment.
Regards
Alan

[JFairman]

Turn up the boost
Sounds like you have a lot of nice stuff including Brian's killer headers.
Too bad you can't put a more modern turbo in there and stay within the rules but rules are rules and they're part of the game.
Of course creative interpretation of the rules always helps. Maybe somebody can take a journal bearing Garret TO4Z (Blowzilla) or Garret GT35 and make it look like a 3ldz.

More timing will probably help and as you know with your 007 fuel head you have enough fuel to safely turn up the boost all the way down a long straight.

[Alan L]

Hi Jim,
I turned up the boost :-)- but the lap times were still worse than a better running car at 0.8. The lag at 4500 is excrutiating - I feel like I need feet on both pedals (brake/throttle) at same time - ie I need to have it nailed to the floor while still in braking zone. Undriveable as a track car. Need to sort the tuning issue. Too many variables - need to get back to my regular track near sea level and start from there. my old lean fuel head would probably have been OK at that track. I always have to lean the engine out about 1/2 a turn on the CP for there. So dialling in another 8% fuel won't help. I kept tweeking the WUR but ran out of races to get it right enough to do anything useful.
Will check no boost leaks first - but I don't think so - no lean off throttle AFRs - just rich all thru.
Regards
Alan