I am planning on swapping the 2.3 head onto my 2.4 block and doing a NA tune. I know the 2.3 head raises compression to i beleive about 11.4:1 or so, which is pretty high already. What i am asking for is an educated guess, or actual knowloedge on how high of compression i can go and still be able to run on 93 octane. I understand all the othe engine mods that will be needed for the swap, to run high compression, etc etc I just need to know how high i can go before i need higher octane fuel. Im thinkin 12:1 or so?? Which isnt much more than what it would be with the swap, so lemme know guys anyone who knows or at least can make an educated guess, no noobs here, I need some reputable knowledge here, Thnx alot guys.
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12:1 will be close to the limit. If you ever see knock you can always get a water injection setup.
Gilles
2.3 Ho
It also depends on your altitude. I once calculated the atmospheric pressure based on altitude here and it was roughly 13.7 psi. So its pretty much a 10% decrease in air density, so, if the relation to dynamic compression were linear (which its not) you could run a static compression 10:1 engine at 11:1. This enables engines to run a fair amount more compression on pump gas at higher altitudes.
Things you could do to prevent detonation are:
Better cooling system
Ceramic coating on piston tops/valve faces/combustion chamber
Cams with more overlap
Lower gearing (higher numerically)
Higher stall converter
Weight reduction
Smaller combustion chamber/dished pistons
I'm sure there are many more methods of additionally avoiding detonation with programmable fuel injection.
But I have a kind-of related question;
People have said that swaping HO cams into the LD9 causes problems with the computer. I'm just wondering how people get away with the head swap and secret cams, but swapping HO cams into a LD9 head will cause problems.
Also why would the cams cause problems in the first place? Does the larger lift/duration of the HO cams screw with the map sensor?
Thanks
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93 octane isn't enough once it starts knocking. Invest in a nice knock sensor gauge.
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one thing to keep in mind about high compression NA, hot spots in the head liek to form, not sure what metal they make it out of but its liek alot of the Velica GTS's like to pop head gaskets cause they run like 11:1 compression which is a bit to much for the car so some spots of the head get to hot and distort alittle to much and then pop goes the head gasket. I wouldn't want to go much higher then 11:1 on daily driver/street driven car
i would say 12:1 max with a good tune.
the ho cam question- its not that the computer cant handle the cams, its that the ho cams make power outside of our rev limiter. our stock cams reach peak hp around 5400 i believe, which gives a nice power curve thru the rev range but falling off a little at the limiter. ho cams make peak power at 6200, our redline is 6250 with fuel cutoff at 6450. this shifts the power range up to high to benefit from it as you would lose considerable power down low in the revs.
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The Celica gts runs at 12:1 compression. That is about the highest I would try to run using 93 octane, but if the motor wasn't designed for it, you might think about getting new sleaves with the pistons and rods.
^
The 2.3/2.4 don't have sleeves and it's useless to get sleeve even on the eco for higher compression.
you can run 15:1 with OEM rods. tuning is the main thing, not parts.
you can run 15:1 with 87 octane like you can run 8:1 with 110 octane
Gilles
2.3 Ho
yup..tuning. ive read that 12:1 is about the max you can run on pump gas, but thats with very good tuning. like a stand-alone/programmable ECU kinda deal.
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ok your using a quad head on your twin cam and im using a twin cam crank on my quad
im planning on using 93 and everyone ive talked to used 93 and had no problems but if i have any ill let you know
Go ahead and see just how powerless you are. .... ROGER THAT!
i think it is shell that has a 94 octane gas. would that help any with how high of compression you can saftly go?
Thanks alot guys, i had figured about 12:1 would be the max on 93, another question i had, would be how much can i overbore do you guys think "safely". How much of an overbore has been used with high compression does anyone know? Im condiering .60 over but only if i can be assured there is enough meat there to hog out an extra .60. Does anyone know of anyone running that much of an overbore?
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there's enough meat to run .060 over.
you'll need a 0.9cc dish on the pistons to get 12:1 with .060 over.
Gilles
2.3 Ho
how much compression you can run depends on cam choice and tuning. Since cams are the biggest factor in how much air gets into an NA engine, they help to determine how much mixture is in the cylinder to be compressed.....
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