max HP on stock internals?

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max HP on stock internals?

Postby jp 84 » Wed Oct 03, 2012 3:11 am

want to know what the stock internals can hold up to and what the weak points are. the goal of my build would to be to push no more than 10psi. would the stock internals hold up to that? keeping in mind that it is a budget build.
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Re: max HP on stock internals?

Postby Nsquared97 » Wed Oct 03, 2012 7:58 am

Your talking with an M20, correct? Pretty sure 10 psi is easily do-able on stock internals, but I'll let others chime in as I'm not a FI expert by any means.
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Re: max HP on stock internals?

Postby Yoshi » Wed Oct 03, 2012 11:06 am

I did 12psi on my first M20 build. I've seen them take 15psi reliably. I think past that you start pushing the limits. 10psi should be fine. would be about 250whp and some change. (completely random estimation mind you)
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Re: max HP on stock internals?

Postby M20_fever » Wed Oct 03, 2012 1:11 pm

Dan Pinder was running 21psi on a bone stock 200k+ m20 making something like 420whp for quite a while with no problems. I'm not saying that's a good idea for a dd, but it shows how stout these engines are. I would be totally comfortable running 10-12psi on a dd, WITH A GOOD TUNE. You can have a fully forged $5k engineering and blow it up quick with a poor tune. So I guess my point is, there is no such thing as a "budget" turbo running more than around 5psi since after that you need a stand alone ecu to properly tune for the power your wanting.
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Re: max HP on stock internals?

Postby blasphemy101 » Wed Oct 03, 2012 3:08 pm

IMO "PSI" isn't a good measurement for how much a motor can hold. 15 PSI means very different things between turbos of varying sizes. The holset HX35 is a common one to use, and people generally push 10-15 PSI (~12 on average) with it. I think 15 PSI puts you well over 300+ whp with that turbo.

Common mods to the motor to prepare it for boost are ARP headstuds, o-ringing the block or head (a few have done both), welding some of the coolant channels in the head, and an MLS headgasket (debated). I don't think many people are running built bottom ends, since they don't make much sense for most power goals with this car/motor. AFAIK, people have pushed well past 450+ whp on an internally stock bottom end.

Most problems (as you can see from the common mods) are related to the head-to-block mating. If you can keep the head on the block and tune it well (these also go hand-in-hand), you can push pretty big numbers on the stock internals.
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Re: max HP on stock internals?

Postby M20_fever » Wed Oct 03, 2012 3:48 pm

what would you consider a good measurement of how much boost an engine can handle?
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Re: max HP on stock internals?

Postby Yoshi » Wed Oct 03, 2012 4:22 pm

realistically. most turbos picked for the motor will be around the same CFM capacity give or take a bit. So 15psi is actually a good really really general measurement here. Unless he picks like a T4 frame or higher but I doubt that.
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Re: max HP on stock internals?

Postby blasphemy101 » Wed Oct 03, 2012 7:12 pm

M20_fever wrote:what would you consider a good measurement of how much boost an engine can handle?


I've just read (on e30tech and other, non-e30 related sites) that boost pressure isn't a good measure and torque/output is a better indication of the forces the rotating assembly will experience.

Yoshi wrote:realistically. most turbos picked for the motor will be around the same CFM capacity give or take a bit. So 15psi is actually a good really really general measurement here. Unless he picks like a T4 frame or higher but I doubt that.


You know better than I do :) it's probably a good estimate for 85% of people who want to boost their e30

I just wanted to point out that making "x PSI = good, y PSI = bad" determinations might not be appropriate. Some people want 250whp, which would require much less than the average you're referencing. In the case of the OP, he's asking about the absolute limit of the stock bottom end, which I think is probably well over the output generated using something like an HX35 pushing 15 PSI.

Either way, you'll blow quite a few headgaskets before you max out the bottom end.
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Re: max HP on stock internals?

Postby jp 84 » Wed Oct 03, 2012 10:17 pm

blasphemy101 wrote:IMO "PSI" isn't a good measurement for how much a motor can hold. 15 PSI means very different things between turbos of varying sizes. The holset HX35 is a common one to use, and people generally push 10-15 PSI (~12 on average) with it. I think 15 PSI puts you well over 300+ whp with that turbo.

Common mods to the motor to prepare it for boost are ARP headstuds, o-ringing the block or head (a few have done both), welding some of the coolant channels in the head, and an MLS headgasket (debated). I don't think many people are running built bottom ends, since they don't make much sense for most power goals with this car/motor. AFAIK, people have pushed well past 450+ whp on an internally stock bottom end.

Most problems (as you can see from the common mods) are related to the head-to-block mating. If you can keep the head on the block and tune it well (these also go hand-in-hand), you can push pretty big numbers on the stock internals.




you talk about o-ringing the block and head and welding some coolant channels?

do u have any info on that or is there any forms on it.
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Re: max HP on stock internals?

Postby Dontrusthise30 » Wed Oct 03, 2012 10:50 pm

Hell if your just looking for 10psi on a t3 flange turbo, you'll be fine. Replace the headbolts and get it well tuned and you'll be fine. I have a completely stock m20 with arp head studs and I've been running 12-15 psi for a year now with no problems.
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Re: max HP on stock internals?

Postby Dontrusthise30 » Wed Oct 03, 2012 10:51 pm

My engine also has roughly 250k miles on it
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Re: max HP on stock internals?

Postby M20_fever » Wed Oct 03, 2012 11:56 pm

i have a welded and oring'd head, i'll post some pics later when i get home.
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Re: max HP on stock internals?

Postby jp 84 » Thu Oct 04, 2012 5:05 pm

M20_fever wrote:i have a welded and oring'd head, i'll post some pics later when i get home.


could you do that i would like to see that done. also what is the gain in doing this?
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Re: max HP on stock internals?

Postby Yoshi » Thu Oct 04, 2012 5:34 pm

oringing keeps the gasket from blowing. welding the coolant channels on the head eliminates a common potential blown HG spot.
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Re: max HP on stock internals?

Postby blasphemy101 » Thu Oct 04, 2012 7:57 pm

To expand on Yoshi's post since I'm bored...

O-ringing: A ring of metal (steel?) is embedded around each of the cylinders on either the head or the block (in some cases both). When the head is installed and torqued down, the ring "bites" into the headgasket, hopefully forming a better seal. The head is typically o-ringed (vs. the block) because it's easier to remove and transport to a machine shop. I don't know if there is an advantage to o-ringing one over the other in terms of performance. I imagine the block might be the better option, because it is less likely to flex compared to the head.

Welding the coolant channels: The M20 head has wide, open coolant channels on the sides of each cylinder. The headgasket has a tendency to expand into these channels under stress. This can lead to a blown head gasket. Welding in the middle of these channels (where they are closest to the cylinder) prevents this from happening.

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