DSP e30 power gainers

[E30 Racer]

I am building a DSP e30 currently. The car is very competitive locally but I feel like I need more power to have any chance at national level. So looking for ideas.
Current car setup:
Engine/Drive Train:
-SPAL Electric Fan conversion
-A/C Delete
-Magnaflow Custom exhaust with High Flow Cat
-Miller Motorsports MAF conversion Custom Heat Shield and K&N
-Miller Chip
-JB Aluminum 8lbs FlyWheel
-CenterForce Stage 2 clutch
-Z3 1.9 l Short Shifter
-3.73 LSD

Suspension/Wheels/Brakes:
-Braided steel brake lines
-HP brake pads
- Custom Valved Koni Single adjustable with ground control coil overs
- Ireland Engineering Aluminum rear shock mounts
-AKG Motorsports Poly DIff, rear subframe, trailing arm and offset control arm bushings.
-Ireland Engineering 22mm Front Sway Bar
-Ground Control Camber Plates
-17x9 Rota Grid Wheels
-Hankook RS-3 tires 255/40/17

Suspension/Wheels/Brakes:

1. Tires. You're on street tires, not dedicated A-compound Hooisers. Size may be OK, if not a bit tall. I like 285s.
2. Spring rates? You don't mention what you have.
3. What's custom about the shock valving? Double adjustables help with tuning for differing surfaces.
4. IE camber plates will probably give you more neg camber.
5. Alignment settings? Don't go crazy with toe out, its not necessary IMO.
6. Front strut brace?
7. Lightweight brakes (front). UUC is a decent option for an autocross car.

Drivetrain:

1. Extruded intake manifold (or custom fab)
2. Lightweight headers
3. Megasquirt may offer some advantages over the Miller conversion, at the expense of tunning hassle (don't mess with launch control or flat shift)

More important, however, is seat time. Get it whenever possible!

[E30 Racer]

Oh yeah, stay away from ITBs on a DSP-legal M20B25.

[Nsquared97]

6. Front strut brace?

Do these make a noticeable difference handling wise?

[Jean]

Do the engine swap, come to the dark side, SM :)

[E30 Racer]

Do the engine swap, come to the dark side, SM :)

OP said he wanted to build a competitive car...

[Nsquared97]

OP said he wanted to build a competitive car...

[Jean]

OP said he wanted to build a competitive car...

It can be competitive, just you have to dump even more $ into it :oops:

[akorcovelos]

Im not really a cone course guy, but assuming you rarely get out of 3rd gear, and probably don't get too far into 3rd, swapping to a 4.10 diff and bringing your rev limit to 7k would probably make the car quicker and more responsive.

Also, pm'd you with a question about your seats.

[Jean]

4.10 would be way too short I bet... for example with m30b35 for me on 225/50/15 v710s 3.73 was WAY short.... 3.25-3.46 would be good though. Some courses do get close to 70mph here... so it all depends.

[brian52555]

I can confirm that 4.10 was way too short with my Getrag and M20.

This is running a few SFR SCCA events, mainly Oakland.

[bmwguy325is]

Click the link in my sig.
I run a 3.65 ratio. I also run 275/35/15s Which are 23 inches.
As for power. As noted the miller MAF was the best power adder I got that is on the cheap side.
You could install a cam gear and the MAF and spend time on the dyno
As for headers Long tube is the only way to go. I currently run the IE shorties but mainly due to the weight savings.
Then as for exhaust 2.5 single all the way back.
The ITBs seem like a good idea. I jut honestly think the cam is not open long enough to take advantage of it.
A larger throttle body can help.
I saw the larger injectors but again you need to tune for them so a miller WAR chip.

[E30 Racer]

Click the link in my sig.
I run a 3.65 ratio.

If you're competing with a 325i/is in DSP, that diff ratio is not legal.

The ITBs seem like a good idea.

Not needed for a legal M20B25. You'll need headwork, a much more aggressive cam, and larger displacement to make it worthwhile (none of which are legal in DSP).

[bmwguy325is]

If you're competing with a 325i/is in DSP, that diff ratio is not legal.

Sorry meant 3.64 missed it by one.

Not needed for a legal M20B25. You'll need headwork, a much more aggressive cam, and larger displacement to make it worthwhile (none of which are legal in DSP).

Ya thus my comment after

The ITBs seem like a good idea. I just honestly think the cam is not open long enough to take advantage of it.

[E30 Racer]

Sorry meant 3.64 missed it by one.

I figured that's what you meant. 3.64 is not legal either. It never came in a US spec 325. The 4-cylinder cars are not on the same line (318is) or class (318i), so updated/backdate is not applicable.

[Wh33lhop]

I can confirm that 4.10 was way too short with my Getrag and M20.

This is running a few SFR SCCA events, mainly Oakland.

Disagree--with my m50 and 205/50r15s (effective 4.27 gearing) I was pretty quick around the past few events at that venue. Given they are rather tight, but I generally rode the limiter once for a second or so with a 170whp m50 at 6800rpm. With a ~140whp m20 and a 7000rpm rev limit you won't be riding as much limiter. Then again I don't mind shifting into third during a slalom either. :p

Also, a faster top speed doesn't necessarily mean a faster time. You'll be ahead on the straight with the shorter diff up until just a little after you hit the limiter, and you'll be deeper in the powerband as you're exiting tight corners.

In the end it boils down to preference and course speed. I'm just saying just becase you're hitting the limiter doesn't mean you'd be faster with a taller diff.

Two examples (At Oakland)



Here I only nudged the limiter once at the beginning of the course. I made use of most of the powerband exiting most of the corners. If I'd had a taller diff I'd be using much less of the powerband.



There I nudged limiter at first, went halfway through third (and I would have had to shift in the middle of a slalom with a taller diff instead of just entering it, or just ride the limiter) and rode it for a second or so towards the end, all the while having more torque on tap for the rest of the course. Again this is with more power, a lower rev limit, and lower effective gearing than we are talking with an M20/4.10.