400HP Build Strategy at Elevation - Mile High
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400HP Build Strategy at Elevation - Mile High Hey All,
I’m planning an LS swap for my 944 Porsche and am trying to gauge whether I can meet my power goals here in Denver with no forced induction. If not, I may need to go with a different swap option.
Goal: 400WHP (944 drivetrain losses 16%)
What I’ll do with the car?: Full restore street car with some autocross.
Complications: Denver is a mile high with an estimated 8,000 - 9,000 density altitude during summer. Which means, we’re looking at roughly 30% power loss by default. Additionally, I don’t have much room for forces air and prefer NA to avoid added weight impacting the 50/50 weight distribution.
I’m hearing anecdotes from folks hitting 400 in Denver however I haven’t come across any specifics on build details for these motors. I’m curious if anyone has recent experience here and can provide guidance on how I can achieve success.
Thinking about this in a different way, should my goal post be 570WHP at sea level to identify a build that can achieve 400 at elevation? This feels like an oversimplification that may not be successful in practice.
Ive been focusing my researching on LS1 383 and LS2 408 motors. My suspicion is that I’ll need to start looking at a 7L to achieve my goals out here and if that’s the case, it may make more financial sense to look at my other swap options (2.5L VW).
I’m planning an LS swap for my 944 Porsche and am trying to gauge whether I can meet my power goals here in Denver with no forced induction. If not, I may need to go with a different swap option.
Goal: 400WHP (944 drivetrain losses 16%)
What I’ll do with the car?: Full restore street car with some autocross.
Complications: Denver is a mile high with an estimated 8,000 - 9,000 density altitude during summer. Which means, we’re looking at roughly 30% power loss by default. Additionally, I don’t have much room for forces air and prefer NA to avoid added weight impacting the 50/50 weight distribution.
I’m hearing anecdotes from folks hitting 400 in Denver however I haven’t come across any specifics on build details for these motors. I’m curious if anyone has recent experience here and can provide guidance on how I can achieve success.
Thinking about this in a different way, should my goal post be 570WHP at sea level to identify a build that can achieve 400 at elevation? This feels like an oversimplification that may not be successful in practice.
Ive been focusing my researching on LS1 383 and LS2 408 motors. My suspicion is that I’ll need to start looking at a 7L to achieve my goals out here and if that’s the case, it may make more financial sense to look at my other swap options (2.5L VW).
Last edited by TonyD87; Jan 15, 2023 at 09:57 AM.
Joined: Apr 2006
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From: Grand Rapids, Michigan
Here's what I would do: I'd go with a 402 LS2, more cubes = more power. You probably have 91 octane up there, not 93, but I'd bump the compression up to 12.5:1. There are guys getting away with 11.5:1 with LS engines at sea level, so I don't think 12.5:1 is excessive. I'd also spec out a cam with a significant amount of overlap, as the exhaust driven induction event will help fill the cylinders. The IVC event will be very important with this build, I would almost want to install an adjustable timing set in order to fine tune the IVC to get your cranking compression where it needs to be.
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One thing to remember is that you don't need more cam at altitude, you actually need a little less. In racing like Pro Stock they have smaller cams for high altitude racing. That doesn't mean don't put a healthy cam in it, but maybe go 230/240 instead of 240/250.
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I would buy/build a 650HP engine to make 400RWHP in Denver. That would be SUPER easy with a turbo, but you don't want one so an NA LS build will cost a bunch more but still totally do-able.
If you want to slap it together yourself, look at a company that makes one already like GMPP, Blueprint, etc and copy that recipe.
*Easy Button
If you want to slap it together yourself, look at a company that makes one already like GMPP, Blueprint, etc and copy that recipe.
*Easy Button
The reason you lose power at altitude is because you lose cylinder pressure. If you increase your static compression to compensate, you're there. Calculate your dynamic compression to stay below 8.4'ish, and it will run like a banshee on pump fuel.
Also, because of the thin air, pay careful attention to quench.
Also, because of the thin air, pay careful attention to quench.
