Serious Question For The Engine Builders

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digginfool
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Serious Question For The Engine Builders

Post by digginfool »

When I bought my LSA, I knew going in that if I ever wanted to build serious power, modifications would have to be made. I've done quite a bit of research, communicated with a few of you, but there is one stumbling block I keep coming across when it comes to building real power with the LSA. Of course, we've already covered the rotating assembly. Yes, it comes with a forged crank and the powdered metal rods are not all that bad, but the pistons are a disaster waiting to happen. If you are going to open up the motor to upgrade the pistons, it doesn't make sense to not go the distance; rods, pistons, stroker crank. It just isn't that much more money. However, as soon as you increase displacement, you run into the next short-coming on the LSA; the 1.9 liter supercharger. You can overdrive it but that builds heat and reduces life. The stock pistons are 9.1:1. Could you compensate a stroker LSA with compression ratio instead of overdrive? For example, go with, say, 9.5:1 or 10:1 pistons to compensate for the lack of extra air coming in or am I looking at this wrong?
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DynaMarine
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Re: Serious Question For The Engine Builders

Post by DynaMarine »

Man Greg I've done 3 LSA builds so far, well let me back up...TKE has done 3 builds for me. 2 started life as Levitator motors and the other a Marine Power.

First one we stroked to 418ci, ported the blower, LS9 cam, crank pulley to add 2lbs boost, 102mm Holley TB, new wiring harness and ECM and lastly and we topped it off with a ZL1 supercharger lid and injectors. All said and done it pumped out 720hp/700tq on a conservative tune. Kolby initially thought the blower would be too small as well and IAT would be to high. Not the case! Actually said it was the smoothest 720hp he'd ever made.

The Levitators we wanted to do cheaper. We kept stock crank and just replaced rods and pistons. Swapped the cam for the LS9 and put a decent tune on it after we swapped the harness and ECM. Even kept the Levitator fuel system. It made 625hp/600tq. Swapping the lid and throttle body and maybe 1 7/8" headers we'd likely see 635-650hp without touching the boost. Again, no issue with the IATs.

Can answer your question on compression, but we've run the stock blower up to 13.5psi boost without issue.
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DynaMarine
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Re: Serious Question For The Engine Builders

Post by DynaMarine »

Here's the dyno sheet in the 625hp LSA
ImageUploadedByTapatalk1448256321.901662.jpg
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Waterthunder
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Re: Serious Question For The Engine Builders

Post by Waterthunder »

Change the pistons for reliability reasons, then the cam (CAN REALLY UTILIZE THAT BLOWER) and overdrive the blower to make more boost. This will make more than enough power for you. Also upgrade the rod bolts or consider a set of Hbeam rods. Plus if you want to lets say help the motor change your rod length an pin height this will help reduce detonation and give you a more boost friendly ring stack.
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Re: Serious Question For The Engine Builders

Post by SWAMPHUNTER45 »

What Dave has suggested makes good sense.

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digginfool
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Re: Serious Question For The Engine Builders

Post by digginfool »

My question is strictly theoretical; I don't have the time or money to try this on my own. My question comes about out of two items I've learned through my research. The first, depending on source, is that the effective compression for a supercharged engine should be around 12.5 to 13.5:1 in order to perform safely on pump gas. The stock LSA uses 9.1:1 pistons and the 1.9 liter blower produces around 8 lbs of boost which, according to a calculator I found, works out to 14:1 effective boost. Any detonation that may occur is controlled by the very capable ECM on the LSA. The other item I learned is that the screw type compressor is very efficient and quiet but unlike a Roots type blower which basically crams air into the intake manifold, compresses the air within the supercharger itself before it enters the intake. This compression creates heat and, if the supercharger is overdriven too much to create enough boost from a small displacement supercharger, the heat produced will reduce the effective compression as well as create a higher probability of detonation. So, that's in the context that I came up with the idea of using higher compression pistons in a stroked motor to offset the small displacement supercharger rather than overdriving, creating heat, and possible other problems down the road. Of course, the best solution would be to go to a larger displacement supercharger but that could run $7-8K as opposed to a set of pistons (that need to be replaced anyways). Just thoughts rolling around in my mind.
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Re: Serious Question For The Engine Builders

Post by crowhater »

dig I have already done this, I have posted dyno numbers and posted youtube video. We made over 700RWHP in a ZL1 Camaro with the factory short block. At this point I knew the factory internals were at their limit so we purchased an ERL assembled short block 416 CI with true 4" sleeves, forged internals, build sheets, and warranty. $6150 for a 416 short block, if you send in your LSA core they give you $2575 back. So you get a built short block for $3575. Because of the true 4" sleeve you can go as big as 454CI on the new short block if you want. They have these in stock in both low and high compression. If you search the WEB you will see the LSA engine has been built to death, the Cadillac CTS-V guys, Camaro LT1, etc. If you do a little reading you can find the parts combination for what you want to achieve.


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