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Join Date: Jan 2004
Location: Sacramento
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Quote:
Originally Posted by JFairman View Post
Someone posted those anti-lag links farther back in the timing thread.
...

...if you've ever removed those steel air injectors on a few 930 engines you'll see that the tips of them are often melted or burned away.
Add more air through them and they'll get even hotter, so where do the melted burnt pieces of steel air injector go.. just where you don't want them - right into the spinning turbine wheel.

Yes, Kenikh posted the anti-lag referance and I gave him credit for it above.

Good point on the blocked air injectors. Have there been any reported cases of these burning off and killing a turbo to anyones knowledge?

If so the best idea would be to get them out of there. Otherwise, air is air if from a pump or BOV and the size of the orifice is going to limit it. However, I have seen a graph somewhere here of the effect on the pressure in the exhaust from the air pump and it's significant on lag.

Good point about pressure in the exhaust. All I know is from the reference article. Maybe the exhaust pressure reduces on throttle lift enough to allow the over-boost to pressurize the manifold.

I am just guessing as I do not know any of this stuff here for sure.

Crazy, crazy ideas I say. (But a fun mental puzzel.)
Old 12-08-2009, 03:32 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
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On my car venting some metered air to atmosphere during upshifts and deceleration through the deceleration valve make the AFR go to 10:1 and it considerably reduces the exhaust popping on deceleration.

My fuel mixture curve is different than most though because I have the IA modified +20% fuel head which runs richer than a stock fuel head during deceleration and B.L. adjustable WUR set for high steady cruise and boost control pressures to keep the AFR's close to normal and not too rich for the current state of tune of my motor.

A friend of mine with a good running totally stock 930 CIS fuel injection tried venting the deceleration valve to atmosphere and his pops more than when it's venting into intake manifold or bypassing the throttle body like stock.

Maybe it's a steady burn after the turbine wheel instead of lots of sporadic explosions in the muffler inlet after the turbine wheel so you don't hear as much popping.
I can't see it so I don't know.
Old 12-08-2009, 03:33 PM
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"Maybe the exhaust pressure reduces on throttle lift enough to allow the over-boost to pressurize the manifold."

If that was the case than the anti-lag process is defeted.

The whole idea of this type of anti-lag system is to is to burn fuel in the exhaust headers to make pressure that spins up the turbo during deceleration and idle.

The exhaust pressure in the exhaust headers to make all that boost during deceleration is going to be way higher than 930 turbo intake boost pressure will ever be so how will you ever get it in there?.

You're burning the air fuel mixture in the exhaust headers instead of the combustion chambers during deceleration and idle with this type of system.

Totally crazy idea on a street car.
If you read on you'll find they did this on certain disposable turbocharged race cars to try and still be competitive with the increasingly small air intake restrictors mandated by the FIA.
Old 12-08-2009, 03:42 PM
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Yes I read all that a couple of times.

One method just pulls timing and adds fuel w/o any air so there is still expansion of the gasses as they enter the manifold.

The air injection system I was thinking was to create a burn in the red hot turbo its self though it dose not note so.

What ever the case, I agree, most aggressive anti lag methods are not fit for the road and probably not for a CIS street car. Though the factory is rumored to have done something on there CIS race turbos in the name of anti-lag.


Still it is fun to dream and learn together.

Bye.
Old 12-08-2009, 04:26 PM
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"Though the factory is rumored to have done something on there CIS race turbos in the name of anti-lag."
Yes, they hired the best drivers with the biggest balls that didn't completely lift and left foot braked... and in the 935 and 962 which had no anti lag crap, drivers like Derek Bell and Bob Wollek anticipated the turbo lag and put their foot in it way before the apex of a corner, or by comparison a bit before you would in a normally aspirated car.
Old 12-08-2009, 04:36 PM
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This is a lot like watching a tennis game....and the ball is now in my court. Screw it, I've changed my mind, I ain't gonna do it. Narry a drop of boosted air will ever make it to my headers. Now, back to your sponsor.....(and still the debate goes on regarding BOV orientation).

What I would love to see some day before I die or become completelly gimpy and paralysed in the left foot, would be for all of us who take the time to drill down into infinite detail, to get together over about a zillion beers (or better yet, Scotch), take the gloves off, and really get down to business.

There is so G D much knowledge out there, what a great way to share it. Thanks all.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 12-08-2009, 04:52 PM
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