97 850 N/A 2.4 20V upgrades/tuning

[puffs01]

i know, people say it can't be done and that just selling an N/A for a turbo is the best idea for making power, but i have an N/A right now and very little intention of getting rid of it. i know stage 0 mods (tune up, new hoses, fixing leaks etc) are the most important, but other than that i would like to know what i can do to make more power. i don't know if anyone does ECU tunes for these models, but i'm shooting for about 200hp if it's possible. my inspiration to try and do the impossible comes from the BTCC 850, and the tribute build they featured on top gear. i saw that they used ITB's from a S85 v10 to make more power and i was wondering if i could do something similar without paying an arm and a leg for it. other than engine mods i intend to install coils, pegasus wheels and new tires and could use some suggestions for a good street tire that won't break the bank. my main goal here is affordability and making a fun daily.

[Clemens]

FCP Euro did a video series where they souped up a NA 850.
Doable, but lots of headache and still not as powerful as a Turbo.
For the same money and time, I'd have way over 300whp with a Turbo.

Btw., the TRW 850 BTCC wagons/cars had highly modified cylinder heads because the stock ones just don't have enough flow.

[dikidera]

You could, but the problem is one other. They likely traded torque for power, meaning that if torque comes to you at 4500rpm, it will now come much later. And since HP = RPM * torque / 5252 we can see that for higher HP, we need to have the torque come much later, which means revving up to 8500rpm which means at the very least, stronger valve springs..

I think you are better off slapping a turbo and going NA-T. With 4-5 psi you can reach 200hp. Of course the if there are any risks it's the piston rings(how much the piston ring gap is and how much the piston itself expands with heat) and the capability of the piston itself to withstand the increased pressures. I think the rods will hold, I doubt they made the rods break with 30 ponies more.

For the NA path - better cams, ported head(you can do it yourself), better exhaust and I would personally do a PS pump delete and go for the electric one, of course better cams means likely trading torque for power meaning before 4500-5000 rpm you would be like driving a 1.2 clio engine but on the 850.

Better exhaust is needed to enhance and potentially move up the exhaust scavenging up the RPM ladder. But you need someone smart enough to calculate where that is.
To get both power and torque e.g best of both worlds you WILL need to install a VVT. For that you will need to buy a 2.4 or 2.5 head from 2000+, port it, and then slap it onto your engine.

The original 2.4 NA intake has the resonance tuned to around 4500-5200 rpm via the long length of the runners, which is around 45-50cm, this is where the greatest effect is. The earlier 850 manifold with dual runners was great to provide torque as early as 3200rpm but was bad at higher rpm(flow restriction). For high hp you would need a shorter intake runner, but you are trading torque down low for power up top.

For the same money and time, I'd have way over 300whp with a Turbo.

Factually wrong, because you will crack the cylinder walls ten times over, only if you are with a 83mm cylinder bore. Without shims or last resort Darton sleeves, you will be capped to max 250.

So what is the consensus, NA-T. I would even slap in the 94 dual runner manifold, a turbo does like flow, but even so it will force it down the throat with this manifold, his torque will be come up at 3200-3300 rpm.

[Chuck W]

Honestly, it sounds like the OP needs to Stage 0 the thing, with maybe a new exhaust and let it be.

Building NA power isn't cheap.

[dikidera]

Like I said, I would personally slap on a turbo with the 94 dual runner manifold.

[Sveedy]

Subject has been beat to death. You can't just slap a turbo on a NA engine.

[dikidera]

Of course not. But it's not impossible. It's even more possible for his 850 since a standalone ECU will also convert it to computer based ignition control and he could probably also go Speed Density instead of MAF.

The Subaru guys have been doing it since Subaru exists.

[Clemens]

.

For the same money and time, I'd have way over 300whp with a Turbo.

Factually wrong, because you will crack the cylinder walls ten times over, only if you are with a 83mm cylinder bore. Without shims or last resort Darton sleeves, you will be capped to max 250.

So what is the consensus, NA-T. I would even slap in the 94 dual runner manifold, a turbo does like flow, but even so it will force it down the throat with this manifold, his torque will be come up at 3200-3300 rpm.

I never meant to slap a Turbo on the NA car, I meant: If you want power, buy a Turbo wagon or car.

[Sveedy]

O.P. is on a budget - doesn't want to spend an arm and a leg. Chuck W pretty much has it. Improve air flow in and out and call it good.

[dikidera]

OP is on a budget and wants some more power that a filter wont increase.

An electric power steering pump will also not cost a lot, this will free up between 3-4hp. Maybe even 5. A tuned exhaust, for higher rpm power, a longer exhaust is required, and also collector length(there are formulas on what and how the relationship is between runner length, collector length and firing rate based on where the exhaust scavenging needs to be modified).

The intake is difficult because there are not a lot of ways to increase intake resonance(the wave that travels back when it hits the closed valves to the manifold runners and back again at the valves, stacking up and increasing pressure thus volumetric efficiency). But perhaps a turbo manifold may help, he will lose torque down low because of the short runners, but gain up top.

A shorter intake path will help too. No, not a cone filter with a CAI, but a shorter path with a filter box. Alternatively a cone filter with CAI but placed in such a way to force the wind pressure inside it.

Bigger TB, if possible.