Garage Storage Organization and Garage Cabinets

kedavis · 02-17-2005, 08:22 AM

Some more interesting reading.http://sdsefi.com/techocta.htm

Frank · 02-17-2005, 08:41 AM

Excellent information. It backs up alot of this I was thinking... which is good.

I mentioned something that could be considered opposite of the following statement...

Quote:

Lowering the compression ratio allows more boost to be run with less retard for a substantial hp gain.

This is because I think that more hp/psi is better then running more psi to get the hp. Not really wrong, but I am just an efficency nut. Of course my life is far from it! hehehehe

Frank

turbovanman · 02-17-2005, 12:04 PM

Hahhhahahaha, Frank, you kill me,

Nice article Kedavis, some more things that make you go Hmmmmmmm!

Frank · 02-17-2005, 12:24 PM

What can I say, I am a typical bored at work engineer.... and I have been reading "Fundamentals of Internal Combustion Engines" by John B. Heywood. Incredible, and just makes me more stupid! hehehehe

Frank

johnl · 02-17-2005, 03:30 PM

Quote:

Originally Posted by kedavis

Some more interesting reading.http://sdsefi.com/techocta.htm

Good stuff. Now I feel MUCH better

beefalobilly · 02-17-2005, 03:50 PM

i've got a G-head and a fast burn, so i'll be experimenting, I think with my light omni and a g head (it's a street car) i'll still have plenty of torque, it's already pretty easy to spin the tires when it's very mildly modified so I'm not too worried.

Johnl, where in california are you from? I'm in paso robles, half way between san francisco and LA.

johnl · 02-17-2005, 04:18 PM

Quote:

Originally Posted by beefalobilly

i've got a G-head and a fast burn, so i'll be experimenting, I think with my light omni and a g head (it's a street car) i'll still have plenty of torque, it's already pretty easy to spin the tires when it's very mildly modified so I'm not too worried.

Johnl, where in california are you from? I'm in paso robles, half way between san francisco and LA.

I am in San Fernando Valley. PM me and we'll meet up. Couldn't get to the TU dyno/tech/BBQ, did you?

johnl · 02-17-2005, 04:27 PM

Quote:

Originally Posted by beefalobilly

i've got a G-head and a fast burn, so i'll be experimenting, I think with my light omni and a g head (it's a street car) i'll still have plenty of torque, it's already pretty easy to spin the tires when it's very mildly modified so I'm not too worried.

Johnl, where in california are you from? I'm in paso robles, half way between san francisco and LA.

I am in San Fernando Valley. PM me and we'll meet up. Couldn't get to the TU dyno/tech/BBQ, did you?

johnl · 02-17-2005, 05:07 PM

Quote:

Originally Posted by turbovanman

Oye!

An engine that has the 782 swirl head and then install the G head will lower the compression ratio. Unsure of the drop but its between .5 to point.

Pros-run more spark advance, can run lower octane gas, run higher boost on lower octane gas, better flowing head than a 782

Cons-less performance off the boost, lower bottom end torque.

Simon -

Your guestimate was about right.

In looking at the posts at "induction - 782 chamber," I learn from "4 L-bodies" that the chamber volume of the swirl is 49-50 cc and the G is 55-56cc, and that the piston dish volume for '85 G pistons is 9cc while for the 86+ swirl pistons is 24cc.

So, 85 G head w/ 85 pistons is 55 + 9 = 64cc and 550cc/64 = 8.59CR stock.
And, 85 G head w/ 86+ swirls is 55 +15 = 70cc and 550cc/70 = 7.86:1 CR for the G head/swirl piston combination.

8.59 - 7.86 = .73 decrease in CR. More than half, less than one.

sergio · 02-17-2005, 05:23 PM

I'm in the process of swapping from a G-headed T2 back to a swirl in my L. The car was fast but, it had horrible mileage (for an L) as I was getting around 21mpg from the set up. Mainly because it would "need" boost about everytime I accelerated, and whenever I was on any kind of incline. Before I stuck it on there I was averaging about 28mpg with the completely stock engine (3" exhaust, g-valve).

Also, I noticed a considerable loss in throttle response when I wasn't driving it "right."

Just some extra food for thought.

turbovanman · 02-17-2005, 05:26 PM

Quote:

Originally Posted by johnl

Simon -

Your guestimate was about right.

In looking at the posts at "induction - 782 chamber," I learn from "4 L-bodies" that the chamber volume of the swirl is 49-50 cc and the G is 55-56cc, and that the piston dish volume for '85 G pistons is 9cc while for the 86+ swirl pistons is 24cc.

So, 85 G head w/ 85 pistons is 55 + 9 = 64cc and 550cc/64 = 8.59CR stock.
And, 85 G head w/ 86+ swirls is 55 +15 = 70cc and 550cc/70 = 7.86:1 CR for the G head/swirl piston combination.

8.59 - 7.86 = .73 decrease in CR. More than half, less than one.

Sweet, now if I could guess at the lottery numbers,

johnl · 02-17-2005, 06:58 PM

Your experience is as suspected. Lower compression ratio is bad for off-boost "around town" tractability.

sergio · 02-18-2005, 01:42 PM

I believe it was compounded by the fact that I'm running T2 electronics as well; since the spark curve is all wrong for the G-head.

kedavis · 02-18-2005, 08:36 PM

Quote:

Originally Posted by sergio

I believe it was compounded by the fact that I'm running T2 electronics as well; since the spark curve is all wrong for the G-head.

youre exactly right the g-head needs a much more aggressive advance than the swirl.

Una · 02-18-2005, 10:29 PM

I'm running a G head on my 2.5L, which obviously came with a swirl head. When I first put it on I had TII (2.2L) electronics. Even with the base timing moved up to 12 degrees (had been at 8 with the swirl head) the car was pretty doggy off boost. Now I have a custom calibration from TU, with a spark curve setup for this G head on a 2.5. Paul actually dialed the spark curve right up to the edge on the dyno, it took quite a bit to get any pinging under boost with this head, he pointed out the curve of the spark advance compared to normal, it's quite a bit hotter with this head. Anyways... The throttle response is absolutely INSANE now. VERY good, and I have tons of off-boost power, tho the throttle is so responsive and my turbo is a bit small, so it's hard to keep the car out of boost. Tho it's a bit easier since I put in the BOV yesterday, bleeds off the boost unless I really get on the gas.

So that's my 2 cents. I think the G head is excellent when the spark curve is programmed to match it. Low end power is VERY GOOD, I don't think I lost any low end power now that the spark curve is matched properly.