turbo...itbs...headaches? yes. Worth it? Yes

[Lil_whitebean]

Not quite done with the car but thought I would post up some pictures of it. My particular build is not super common and thought others might like to take a look.

Car is a 87 325es
m20b25 motor refreshed pistons, gaskets, arp studs and hardware etc. Stock compression.
AN lines all around for fuel, including upgraded pump, pressure regulator, fuel rail, injectors(650cc) etc.
Car has upgraded mounts all around, brakes, brake lines, GC suspension, swaybars, cooling system overhauled...

Everything basically garagistic sells for this car and tons of other parts

RHD ITB kit with ECU masters standalone
CxRacing V2 turbo kit, ball bearing GT35 currently on spring pressure 8psi

This week we are swapping the plenum for something aluminum, upgrading clutch, flywheel etc and installing the sikky booster less setup for the brakes. Then finishing the tune in 2 weeks on 91 and on E85

[Panici]

Curious why you went with ITBs just to slap a turbo on? A pretty uncommon setup.

Does it make any difference to throttle response or spool?

[McGyver]

Yeah, that's a pretty wild setup and a super cool looking car!

I'm also interested in why you have ITBs and FI. I always thought that FI would surpass any gains from ITBs, so a stock or modified manifold with a single TB would be good enough.

[82eye]

wild !

[zwill23]

I remember KAMotors doing something like this years ago and someone commenting, "You do this so you have more throttle plates blocking flow" lol. Jokes aside, I bet the intake noise is the real reason to do this.

[Panici]

I remember KAMotors doing something like this years ago and someone commenting, "You do this so you have more throttle plates blocking flow" lol. Jokes aside, I bet the intake noise is the real reason to do this.

I just wonder if you'll get that much intake noise with the throttles plumbed into an intercooler instead of free air?

[zwill23]

I just wonder if you'll get that much intake noise with the throttles plumbed into an intercooler instead of free air?

I'm sure it would be muted, but you can still hear the ITBs with a plenum so I don't see why adding a turbo would change that. We'll just have to wait for lil white bean to give us the full review...

[Lil_whitebean]

So the original idea was to just do an NA build with ITBs, I found the car to be amazing once that version was running, great throttle response, the noise coming from under the hood was SO good, that for a short time I even ran It without a hood.

However the car was too well sorted, too predictable, too stable. I wanted more power, so then the idea was to build a 3L+ stroker but once I started weighing the cost I found FI to have the potential to be more exciting. I also like odd different things, my stubbornness to not let go of the ITBs has driven some long nights both with sourcing parts to make sure everything works as well as with how to tune it.

I also come from the world of motorcycles, where basically everything has an ITB, sprinkle in some fascination with motors like the RB26 and you have a stubborn person that will do too many stupid things to make it work. Lucky for me my friends shop was willing to entertain my experiments and I found a tuner here in San Diego that had no problems with the car.




Update from last time is that the car did get the brake booster delete installed, it got a base tune with the current carbon plenum and made 375whp on 11psi with 50% E85. We dialed it back to about 340whp since when we did the tuning failed to turn up the fuel pressure regulator by the end of the session we were pretty high on injector duty cycle and it was getting late. She wants to make all the sauce, car should easily crack 450whp+ with more boost. We also upgraded to single mass flywheel and stage 2 clutch.



Also there is some oil seeping from in between the head and the block on the intake side, going to pull the head off, refresh and add a cometic head gasket, plenum, flex fuel sensor, and then head back to do the final tune.



Just shy of 350whp and its a rocket, makes all the right noises hooks up really well, throttle response is still so crisp and it makes really good usable power out of boost which is nice, its not a slouch.

[Lil_whitebean]

a couple stills from the dyno

[AWDBOB]

Are you chasing more power eventually?

Not hitting 200hp until 4900rpms seems like you have the wrong turbo for the setup

[e30davie]

Pretty neat setup. Must be a riot to drive.

The Nissan skyline GTRs as you mention, and pulsar GTIR were individual throttle and turbo. So there must be some benefit.

[Lil_whitebean]

Are you chasing more power eventually?

Not hitting 200hp until 4900rpms seems like you have the wrong turbo for the setup

Yeah, the idea is to be somewhere around 500hp, also for this tune timing is not aggressive. Depending on how this does I may or may not swap out the hot side of the turbo for something that will spool a bit earlier.

If im being honest though the car is actually very daily drivable because the power doesn't come on until later. I have had 4-500hp turbo cars that make high power closer to 2.7k rpm and while they are fun to drive they are always "on" so I dont really mind the lag, it makes you feel purposeful when ramping up rpm or dropping a gear.