Maximum HP onan NA M20

[NI_racing]

I am in the process of building an 86 4 door 325e. I will prob do the E bottom to I top until i get a turbo sourced and configured. I am expecting somewhere around 175 to 190 after the E to I Hybrid swap. I do plan on switching the pistons, cams, and springs to handle the extra rpm and HP. My question is tho, how much HP can you make out of an M20 without going Forced Induction or Nitrous? Just looking for straight up engine power. I assume that its not much more than 200-210 since everyone ends up going turbo or a 50 swap. Also curious as to the expense of building said NA motor? Thanks

[NC325iC]

200ish

[Erick]

There are stroker kits that'll take it up to 3.1l, but at that price point, you might as well do a swap or boost it. Unless you really want the sleeper look, even under the hood.

[Justin B]

I've figured that at the wheels, with a 3.12L stroker, ITB's, and everything just right, I could potentially put down about 220. The price is ridiculous though to build it similarly.

If it was for an E30, I wouldn't bother.

[nando]

people here just go about it all wrong.. if you really want to know how to build an M20, hang around on the e30zone.net forums. you can make a lot more than 220hp, but everyone here likes to build a huge motor with weak compression, a mild cam and stock engine management.. and don't forget to add the restrictive exhaust! meh.

that said, I realy doubt a standard 2.7i will make 190whp. it's most likely going to be in the 160whp range.

you don't need ITBs for big power either...

[NI_racing]

Thanks guys. I have every intention of boosting, i was just curious as to the alternative

[lifeiskaos]

boost ftw. hp:$ ratio is loads better than any NA m20 application

[Justin B]

220 at the wheels is a lot more than that at the crank...sure 10:1 isnt 11 or 12:1 compression either, but each point of compression doesn't raise the HP very much. A couple percent.

FWIW, thats my goal, I'll be stoked if its higher, but I kind of doubt it will be more on the ground. Wild cams could make it higher, but something streetable that's useable would be something like my MM Rally cam. ITB's help if they're built properly with the right dimensions, and anybody who builds a real stroker with stock exhaust is an idiot. /me in this thread

[nando]

cam/compression go together. No, the static CR doesn't make a big difference in power by itself, but it will if you couple it with a more agressive cam (higher CR + more overlap/duration = higher MBT). That's the big issue here - sure, you can build a 3 liter M20. But you need to get the thing to breathe in order to make serious power, and breathing is a big deal when you have a 2v head.. that's just not going to happen with an MM rally cam and less than 10:1 compression. I made similar mistakes on my build, and I'd change a quite few things if I were to do it again.

Otherwise you are left with a warmed over M20 that feels strong but never really feels fast. ITBs and all that crap are just bling, unless you are running a wild race cam you're wasting your money, on top of the fact that the power bands most ITB setups (and the cams that match them) are built for are way past what a "streetable" M20 is capable of.

Not trying to attack your ideas (I don't even remember if you posted your "recipie") just sharing what I know from my own experience with M20s.

[NI_racing]

So nando what recipe would you cook up for a streetable NA m20?

[asubimmer]

200ish

lol not even close...

[nando]

So nando what recipe would you cook up for a streetable NA m20?

Like I said, I'd have a look at the e30zone.net forums and see what they are building. Look for a guy from australia making over 250hp on a dyno dynamics.. you probably won't want to copy it exactly (I'm sure it was $$$$) but it may give you some ideas of what direction to go.

[NI_racing]

good deal. I'll have to check that out when im outta work, the filters wont let me access it....