MyE28.com

Looking for some words of wisdom. I hit the Dyno today to finally see what my turbo m30b35 makes. It has a 13lb wastegate spring so that’s the starting point. It made 270hp/300tq. The delivery looked nice and smooth but I felt 13lbs should have made more power. We upped it to 17lbs and again....exact same result of 270hp. I was told there must be a restriction somewhere to not have gained a thing after adding 4lbs. Before throwing money and time at this I wanted to poll the audience. I don't know if it’s my exhaust size, the aftermarket cat is crap, it’s my log manifold or something else. I am prepared to kill the cat, get new manifold and go to 3” exhaust but rather not do all of the above.

2.5” charge pipe
2.5” exhaust with a cat
1.5” log manifold - it’s all 90’s & T’s so the entire thing primary/secondary runners all 1.5
HX35-7 blade
MSPNP2

My buddy with an m30b35 turbo had the same EXACT problem as this. We eventually chalked it up to the valve springs not being stiff enough. We changed a lot of parts along the way. It wasnt until we put in an entirely new head with stiffer valve springs did we get the power numbers we were expecting.

That’s not quite the response I was hoping for. I took the head off last year lapped valves and replaced seals. I never checked or replaced the springs and it has 210k on it. I am building another motor and again never checked springs. I’ll have to read into how to test these now before putting back together.

I will add that first pull was 13lbs on spring only and tapered down to 11lbs of boost by 6K rpm. When we upped to 17lbs it also tapered from 17 down to 14 by 6K. Additionally around the turbo would blow plume of smoke at end of 2nd and 3rd pull. Nothing on first one. The guy running Dyno said it was blow by. I don’t know how blow by would come from around turbo unless it blew out a gasket allowing exhaust gas to escape.

Sorry its not what you're expecting but its what the problem is. The rocker springs are not strong enough to seat the intake valves with the additional boost pressure. Or the backpressure from the turbo is not letting the exhaust valves seat. Could never figure out which was the actual problem but stiffer springs solved it.

I think we installed Ireland Engineering springs, I would recommend a set for your new motor.

Appreciate the input. I’m going to take the cat off and see if it’s garbage. If I can’t find anything else glaring that’s robbing me of power I will just have to wait to swap in rebuilt engine.

Without the two curves, we are travelling blind. A difference in boost level should have changed the shape of the curve. How much different is the curve, especially with regards to torque? What has changed with the torque curve with the different boost level--aka put the two urves on top of each other? What is the difference in timing with the new boost level?

Just some other thoughts from what's been said aready: I would also suspect that turbo might be on the small side and you have either ran past the efficiency island and you are losing power simply because as you up the boost you are moving in the wrong direction on the curve.

Do you have a boost controller? It would seem that you might have wastegate creep where you are losing torque build due to premature openeing, or maybe you have simply reached the limit of flow of the log manifold and small turbine wheel where.

Like it was previously mentioned. posting some pics of your dyno pulls would be super helpful. Especially if you have one that has the afrs and boost plotted up. Having ran a very similar setup here is my input.

I dont think the valve springs have anything to do with what your experiencing, 20psi should not be forcing your valve open. I think seat pressure is 70 lb, so on a stock 2.7 sq inch area intake valve that is like 54lbs of static pressure from the intake. And ofcourse that does not factor in the much higher pressure on the opposite side of the valve.

What size exhaust housing is on that holset? Is it a t3 or t4 flange. I had a 16 cm^2 housing and it was a t3 hybrid.

That holset is a diesel turbo so increasing boost will increase flow into the 35 psi boost range. I think dsm guys make 500 plus on evos. You should be making more power with boost on that turbo.

Now you mention your manifold is a single 1.5 inch log, that might be a restriction depending on how well the manifold flows at the flange to the turbo.

Another idea, are you sure your clutch isnt slipping. You didnt mention an upgraded clutch but i think the stock unit becomes limited around 350 whp? I had an m5 clutch so i never reached the point of slipping.

On my setup i had flipped log manifolds with a y adapter. I never did hit the dyno but i ran a 14 psi spring and theoretically i should've been ,making 350 to the wheels i believe?

7 blade HX35 with 12cm^2 exhaust housing
T3 flange is welded on front of log, flow prob not greatest
M5 clutch as well
Wastegate has 13lb spring and using EBC for added pressure
Not sure how to add attachments on this forum but ignition and dyno are on bimmerforums where I have similar thread in FI section
https://www.bimmerforums.com/forum/show ... more-power

it's his timing. it's crazy low.

Anyone have ignition map they can share to give me a ballpark of how high this can go on 93?

i've been reading your other thread on bimmerforums
start at 18* at least with base boost. 13psi you can probably use stock timing.

your exhaust stuff is for sure killing power and the boost drop off is 10000% killing power but
from 14 to 17psi stays the same start with the easiest test. Timing is hardcore looking at me right now.

also, yes the turbo is on the small side and when you need a better turbo there is allot of people
running vsracing turbos look into those they're china, but they are the good china kind.
i think you're on a budget like allot of us. they are crazy cheap. i'm going to get one pretty soon as my hx40 close to max.

I figured since you were getting tuned it at dyno shop the tuning of timing wouldnt be an issue. I would find a new tuner to go to, the whole purpose of a dyno is to have a stable way of approaching max timing at wot.

for a base map i used Brad D's map from his dyno tuning session. I did some street tuning and slightly tweaked it. If you go look in his megasquirt thread you should be able to find a picture of it.

Alright so I basically have the same setup, I'll share with you here
Junkyark B35
Flipped cast manifolds to 1.25" schedule 40 pipe with a T3 flange
Boostlab 6262 turbo .83 T3
2.5 Charge pipe
3.0 downpipe to stock exhaust
60lb injectors
93 pump gas
Diypnp 55 pin Megasquirt

I made 320hp 351lbs @ 12psi at sea level
It made 400whp at 20psi when I forgot to hook up my wastegate vacuum line
Something is wrong somewhere

Valve springs too soft...blowing the valves open...













That ain't it chief.

turbodan wrote:Valve springs too soft...blowing the valves open...

That ain't it chief.

Intaker