Das Beast: My E30 track / street build

[dvallis]

Rereading old Das Beast blog posts is fun. Glad we weren't this guy on the dyno.

[dvallis]

Car is in for graphics at Sign Effects in Austin. The owner Beth is a BMWCCA member who has had many BMWs over the years. So glad gearheads are doing the job.

[dvallis]

Turbo Revisited

We want the turbo to spool faster. Back to simple physics: Take the same mass air flow, send it through a smaller tube, you get higher velocity and the impeller spins faster.

We're hoping this new 0.58 A/R housing isn't too small, but we'll see. Tuner thinks it will be fine, since it's T4.



In the meantime, here's some turbo math.

1. Our turbo compressor has a 0.7 A/R, 62 mm inducer, 82 mm exducer, 2.5" inlet, 4" outlet.
2. Pressure Ratio is (19 + 14.7)/14.7 = 2.3
3. Flow is 420 HP / 1.44 = 292 CFM x 0.078 = 23 LB/MIN

Since PTE are (cough - unhelpful) they won't provide a compressor map for the 6262 or even tell me where I am on the map.

I found a compressor at Garrett that's pretty similar: GTW3684R. Map is below. We're on the middle left side at PR 2.3 and Flow 23. Not totally ideal, but not way off the map in the boonies either.



We'll see how the new turbine housing does. Will get that downpipe exhaust leak fixed and have the downpipe ceramic coated while we're in the process.

[citizen_insane]

I think your estimate of compressor flow is a bit on the low side, but none-the-less, the turbo is oversized for the amount of power you're making now. You really don't want to be riding the surge line. If you are planning to stay at this power level, a smaller turbo with a 76mm compressor exducer would probably be a better fit than your current turbo with a much smaller A/R housing. Going to lower A/R will help with transient response from a flow perspective, but you're also going to shift the turbine's peak efficiency to higher expansion ratio which means at very low ER, efficiency will be pretty bad. I'm not sure if you have turbine maps available, but you may find that going really small on the turbine may be a losing proposition, but I can't say for sure without seeing the maps of the wheel w/ various A/R housings.

I'm guessing you're already familiar, but I find it very useful for an off the cuff estimate of turbo estimates. I realize most of the data is likely not available, but these reasonable guesses will get you closer than approximations like 1.4-1.6 hp/cfm.

https://www.borgwarner.com/go/2J4V2B

Closes map I could find (BorgWarner S300SX). Ideally your peak power point would be somewhere closer to the red star I marked on the map.

[dvallis]

Yep. I'm with you on that. PTE won't give up the data so we're going to "try it and see". Under 2K RPM we'll probably be riding the surge line, but I'm not too concerned since it's partial throttle. At WOT flow builds -fast-, even with a 0.84 turbine, so we get into a good part of the map quickly and stay there. The 0.58 turbine will spool like a maniac. If it gives us the flatter torque curve and if the compressor doesn't explode, we've got a win. The PTE rep didn't freak out and say "Never put that 0.58 turbine on a 6262" which is good. They may have even tested the two together, LoL. Our tuner has a lot of practical experience and felt a T4 0.58 will flow enough for the 400ish HP target. Also encouraging. Like I said, we'll see.

[dvallis]

Graphics are coming along. Here's a proof of the stripe colors. Looks even better in person, given monitors not being calibrated and all that.



Graphics guy did a paper template to get a feel for how the vinyl will lay on the car.







The stripes are printed and have to out gas VOCs for a couple of days. Also waiting for it to warm up. Monday is the plan. Will be 75 and sunny in Austin.

[dvallis]

BMW E30 DAS BEAST

Graphics package by Massive Lee. BMW stripe and vinyl install by Sign Effects in Austin

[ForcedFirebird]

Looks great. When is the first test sessions?

[dvallis]

Soon .... freaking soon. :-) Installing the smaller turbine, fixing the downpipe leak, permatexing the oil pan then back to the dyno.

[Digitalwave]

Awesome!

[zaq123]

very very nice. It would look cooler with proper headlights IMHO but still looks killer

[dvallis]

Had a couple of free hours today and put 50 miles of city driving on the clutch without boost. Will break it in for about 500 miles before the next dyno run with smaller turbine.

Some observations:

I need more fooking padding in the seat. Ow!

Engine is damn smooth after the dyno tune. That big six sounds awesome when it gets going.

Clutch is very street friendly for being a multi puck ceramic

We need a manual choke for five minutes after startup. Once temp starts to register on the gauge, idle is beautifully smooth at 800 RPM. Definite tuner value add.

Oil pressure hot is 20 psi idle, 50 psi cruise

15 gallon tank was 1/4 full but only took 6.5 gallons to fill, not 11. Need to look into the gauge & sender.

AFRs are very steady at any given engine load after the tune.

Engine pulls about 9 psi vacuum at cruise (38 kpa)

[dvallis]

Worked on some final punch list items today. Took the driver's door off for better access to the foot well and dash







First thing we did was fix the speedo. We must have had bad data for the wiring. Proper diagram for VDO is shown below.



Working now, and we have an odometer. Speedo needed to be programmed with the K factor, calculated as 7340. See this post from way back when for speedometer math. It's dead-nuts accurate, cross checked with a GPS speedo app on the phone.



Fabricating a new dash support bracket



Now that's solid, and easy to get on and off.



Start of the new dead pedal



Getting there



Looking good



Perfect fit

[Elysian]

Car looks amazing, hope I see it around town at some point

[Digitalwave]

You don't need a manual choke. Megasquirt has a ton of control over after-start and warm up enrichment. My car is better on cold starts than it ever was with Motronic.