Kory-88Iroc 350 tpi

I'm going over the planning stages of a 6 liter ls1 swap. I have read quite a few posts on the subject. In one in particular some of you were mentioning gas mileage. If I read it correctly most of the posters were getting between 28-30 mpg on the freeway. If this is correct my question is Are you guys keeping the displacement on demand functional on your engine swaps/ Is it even available on the engines you used. The reason I ask is that I have been thinking of running the 6 liter with megasquirt. Do you think this would adversly effect my ability to get good mileage on freeway trips? Are there other things about the stock computer that would be better for mileage? One of the reasons I'm considering this swap is that by the time I'm at the power level that I want with my lt1 Mileage isn't real good anymore. I know that the ls1 engines are supposed to be able to run bigger cams without seeming like they are. Ie better street driveability and mileage?? When I started my le swap I wasn't concerned with gas mileage (gas was around 225 a gallon) Now with the current prices and future prices I find that it is becoming more of a factor. I know that driving habits effect mileage, I would just like to have the possibility of making my gas go farther if I drive nice. Any thoughts would be appreciated. Kory

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88Iroc lt1 355, mahle pistons, compstar 6"rods , stock crank internally balanced, 4 bolt studded block, Advanced induction dominator heads Ai 22x/23x cam, holley 58mm tb, 1.6 comp cams rrs,home built equal length lt headers,custom built cat back,t56, street twin, hurst shifter, ls1 brakes front and rear. ronal r15s, homebuilt 8.8 rear fms 4:10 gears. Dyno numbers and new track times to come.
Hotrod air underdash A/C and 01 ta dash new for 09.

bnoble

This thread over at ls1tech might be of some help. The biggest differenct I can see between megasquirt and the stock PCM is that megasquirt utilizes batch fire injection, whereas the stock PCM is sequential, which allows much greater control over low speed fuel delivery. This is how they can run those big cams and still manage to idle. I know this also helps somewhat with emissions, and probably with economy as well.

As far as displacement on demand, If you're referring to the LQ4/LQ9 engine, I don't believe that feature is available on those engines as from what I can remember some type of hydraulic mechanism was used to disable exhaust and intake valves in unused cylinders.

I'm kind of in the same situation as you. I'm researching the possibility of a 6.0L swap and looked into the megasquirt as a cheaper alternative to a factory PCM, wiring harness, and tuning software. It appears that most everyone running Megasquirt on an LS1 is running it along side the factory computer though, although control of the 4L60E trans through megasquirt looks like it isn't too far away.

Kory-88Iroc 350 tpi

I could do it pretty simply. I have a t56. I think that it won't be long before they can do sequential fuel injection either.
Thanks for the reply.
Kory

MrDude_1

no genIIIs (aka LS1s) have DoD.... so the MPG you're seeing with LS1 swaps is with it firing on all 8...

Kory-88Iroc 350 tpi

Mr Dude,
Do you think that using a megasquirt would adversly effect mpg?
Thanks,
Kory

MrDude_1

i know it will not have a significant effect.. but it is slightly less.

you dont get Decel Fuel Cut Off... you dont get a 14.6 AFR with a PE.... ect...

but realisticlly, in the real world, your tire pressure has more effect on that MPG then swapping to MS... so its not really significant.

Kory-88Iroc 350 tpi

Thanks for the info.
Kory