Unless there are other engine blocks stamped with G4CS and my 1990 Talon TSI came with a different head than a 4G63, I am positive that is what I have, but anyone is welcome to visually inspect and verify. I don't have a problem with that. The pistons are the G4CS SOHC types. The compression measures 220psi at 6000 feet altitude. By my math the compression would measure ~270psi at sea level. I would not try this engine build at sea level unless you use larger cams to bleed some compression off.
I took the car to Cripple Creek for some gambling over the weekend. It did good but it did get some light detonation climbing the hills at part throttle. I notice the fuel map is too lean in that area, so I fixed it. I did have a scare when I came out to the parking garage the next morning and noticed a big oil spot under the car, but my oil is full and the spot didn't look fresh so it must have been someone else. I need to check parking places better before I park next time.
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Nice, You don't happen to be on hybridz too. do you?
I'm on hybridz and several other sites with the same login. I have seen some of your posts over there.
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What kind of timing are you running up top?
I'll have to look on my laptop to see, I don't remember off hand. I pulled a lot of timing with this build from my old 2.0 spark table.
I don't see why this is so hard to believe. ??? It's always been common knowledge that it's knock that kills sirius pistons, not cyliner pressures. We all know what e85 can do. The benefits of e85 are not for engines that are built for pump gas. For example, it starts to dwindle the fuel mileage difference once we realize how much compression can be run regardless of boost and still see good results without detonation. Taking advantage of such high thermal efficiencies is what the major manufacturers are doing wiht direct injection so that we can still be reliant on fossil fuel. But, in the OP's case, no expensive direct injection fuel injectors with special mounting locations after the intake valve, and no super high pressure pump is required to boost at a high n/a compression ratio.
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Matt
dd '90 GST, Holset H1C
From the thread in the newbie area it came to my attention to point out that you need an 8 valve 2.4 block with the 4g63 head to arrive at this compression. The G4CS I used was 8 valve. If you use a 4G64 then it needs to be 8 valve, so truck, van , etc.
That will give you this piston which is basically a flat top with 2 valve reliefs:
The car is still running good. Still waiting on my friend to get his car back from paint. I've put around 3k miles on it now and I love the low end performance for daily driving.
This thread has inspired me to run my 2.4 in my n/t car. I've been doing so much research and then just came back and measured my piston dishes for my 2.4 4g64. It is 15cc DISH. Swapping a 1g or 2g 47cc head onto this block will not alter the compression that the motor originally had from the factory: 9.5:1 (per the 2.4L FSM).
The DOHC 2.4 motor has a head identical to the 2g head. Head volume and all.
Here is a pic of the 4g64 DOHC piston beside an n/a 4g63 piston:
Look how healthy that 4g64 "SA" dish is. No need to worry about valve to piston contact since the n/a 4g63 piston has so much less dish. The valve reliefs of the n/a 4g63 piston are much shallower than the dish of the 4g64 "SA" piston.
So again to verify. IF you have a 9.5:1 CR (from the factory) 4g64 that had the DOHC head, then you can swap dsm heads all day long and your CR will be 9.5:1 not +11:1.
Thanks for updating. I only ended up with the higher compression by using the 2.4 SOHC pistons. BTW, my engine is still running good at 14psi boost. I still love the way it drives and the off idle response it has.
I have been reading this thread and i have a couple questions? First what years did the 4g64 come with a dual overhead cam? Is this a 6 bolt or 7 bolt motor the dual over head cam version? Next, can the sohc motor except the dual overhead cam pistons? Third is 9.to 5 to1 hard to control on a stock eprom with a modified timing maps for higher compressions? I am also curious what you think about running a cyclone intake on this as well a torque spooling monster.Just looking into possibly doing this bottom end swap to gain more power in my automatic awd.
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James Chanley 1992 AWD Automatic
