KHShapiro

iTrader: (10)

anyone care to list the cam they are using?
i remember reading a while time ago about some specs but the search isnt working atm so anyone want to post up
114+ lsa
Turbo only.

engineermike

This should be entertaining if people post up.

Mine is 224/236-114. 388 LTx T76GTS. 9.92 at 146 mph full weight 16 psi boost.

Pro Stock John

iTrader: (34)

234/234/114

Rusted40

I'm using a straight pattern cam 235/235 114lsa boost/backpressure 1:1
it was a 255/262 114. it had an insane powerband above 5000rpm

I'd say reverse splits for small turbine
straight pattern for low(?) backpressure
mild split patterns for drag

I have a friend who ports heads for a living who sez some turbo engines like lots of overlap and or low lsa. also to install it "straight up". no advance.
way too many variables to make blanket statements.
it seems everyone with a turbo tries multiple cams


flamesuit: ON

KHShapiro

iTrader: (10)

well to be fair ,single pattern here
244/244 115 lsa

stevieturbo

so which was it ??? 235/235 or 255/262 ???

engineermike

He started out with a 255/262, then later switched to 235/235. The backpressure/boost ratio with the big cam was 1:1. I'm curious if the backpressure/boost ratio changed with the smaller cam. I have a crazy theory about alot of overlap actually helping the boost and backpressures equalize.

Pro Stock John

iTrader: (34)

1:1 backpressure sounds pretty good right.

DRCE

Depending on transmissions as well. I like reverse split stuff for automatic cars and single patterns work great with manual trans cars.

stevieturbo

Not if its at the expense of EGBP bleeding into the intake charge, although its unlikely.

I was under the beleif, if you can obtain 1:1 or indeed less...thats ht ekey to making huge amounts of power, and is how the old turbocharged 1500cc F1 engines made so much power.
In qualifying trim, they were making around 1500bhp from a 1500cc engine. Not too shabby.

KHShapiro

iTrader: (10)

go on...

MawneeC5

iTrader: (12)

Pro Stock John

iTrader: (34)

I thought 2:1 backpressure was bad.

Got Me SOM

iTrader: (2)

my thoughts exactly...

engineermike

This is exactly what I was getting at. If both valves stayed open a long time, then the boost pressure and backpressure would equalize, making the ratio 1:1. Better for power? Probably not. It would be like running an open pipe from the header to the plenum.

By shortening duration, the Backpressure/boost ratio might go from 1:1 to 1.5:1 but gain hp in the process.

This is just a theory.

Mike

KHShapiro

iTrader: (10)

interesting theory

stevieturbo

Until you can achieve a PR of 1:1 or less, I cant see any reason why you would want overlap ( using that term loosely ), to allow exhaust gases to enter the cylinder, or even worse, the plenum.

engineermike

stevie, I used to believe the same thing. However, a few dyno tests that I've seen seem to indicate otherwise. For instance, INTMD8 did more turbo cam testing than any one else I've seen. He tried at least 4, maybe 5 different cams on his 850 rwhp twin turbo LTx. He was running a 2/1 backpressure ratio and every time he added overlap, it gained power. I would be very interested to see just how far you could go with it, though.

FormulaFire

iTrader: (20)

234/228/116 reverse split

Pro Stock John

iTrader: (34)

Another aspect to Intmd8's LT1 project car is that he's been going for as refined a combination as possible. Mike, I recall that he's swapped out cams that made more power for milder cams, but did that to increase the driveability.