M20b25 late spool. Please help!

[OmarE30]

Hello everyone, so i finally finished boosting my E30 and I’m having some issues with the turbo spooling late. I’ll have boost come on around 4500rpm I’m only pushing 9psi

Current set up
-M20b25
-3.15 gears(don’t know if this would affect the spooling)
-hy35w(should be a quicker spool)
-46mm precision turbo wastegate
-ms2pnp
-cxracing exhaust

From my understanding i should start seeing boost build up around 3500rpm and with the hy35w(9cm housing) it should be sooner?

I’ve done a pre-turbo exhaust leak test and found out the turbo flange has a slight leak. I would assume the leak would have to be very noticeable for it to be spooling so late.
I haven’t done a intake side leak test yet but could that cause a late spool?
Even if i don’t see the boost on my boost gauge, I would assume that even if i had an intake side leak that the exhaust should still dump when it hits 9psi because of the pressure built up in the exhaust manifold and i do here it dump but it’s only around 5500rpm and up. If that kinda makes sense.????

Hopefully someone can help me.

[e30davie]

It might pay to post your fuel and ignition map. and have you verified your ecu timing settings with a timing gun?

[OmarE30]

It might pay to post your fuel and ignition map. and have you verified your ecu timing settings with a timing gun?

I verified my timing and had my car tuned before the turbo so it was running well. I currently don’t have the map sheets I’ll upload them as soon as i get them.

So i did a boost leak test on my intake side and i had a pretty massive leak. I ordered the new intake boot to repair it. Would the intake leak cause a late spoil?

[Dgerry]

Yes it will, and it doesn't take that big of a leak either. hopefully that gets you going.

[OmarE30]

Yes it will, and it doesn't take that big of a leak either. hopefully that gets you going.

Thank you for the information and help I’ll post update as soon as i get the parts.

[e30davie]

I verified my timing and had my car tuned before the turbo so it was running well.

Did you get it tuned with the turbo...?

[OmarE30]

[QUOTE=e30davie;4893616]Did you get it tuned with the turbo...?[/QUOTEnot

Yet, as soon as i get the boost leak fixed then i will start tunning. What AFRs should i want to hit while I’m boost and also ignition timing?

[Q5Quint]

What AFRs should i want to hit while I’m boost and also ignition timing?

Are you asking about target AFR for your closed loop trimming, or your open loop table values you are gunning for while tuning?

Not sure what equipment you are using but you probably want 12.5 for WOT and on-boost open loop, 13-14 for part throttle with no or little boost closed loop, and maybe 15-16 for whatever your highway cruising with your cruise control rpm is off boost closed loop and idle open loop. Most will set it at 11-12 for anything over a certain rpm and boost/fuel load for safety factor in case of overboost from a stuck wastegate.

You need to get your closed loop table settings right so if your fueling table is way off from your afr table the computer doesnt 'hunt' around adding and removing fuel to try and hit an afr you are not actually tuned near.

Something like this:


Note how the highway cruising is at 14.6 until you push the pedal for more fuel and it goes back rich to 11.4afr at just 200rpm. Note that 100% fuel from 6 42lb injectors should be around 400hp.

You can also use this tool to generate an AFR table: http://www.useasydocs.com/theory/afrtable.htm

From the safrtool website:

6 AFR - Rich Burn Limit (engine fully warm)
9 AFR - Black Smoke | Low Power
11.5 AFR - Best Rich Torque at Wide Open Throttle (WOT)
12.2 AFR - Safe Best Power at Wide Open Throttle (WOT)
13.3 AFR - Lean Best Torque
14.6 AFR - Stoichimometirc Air/Fuel Ratio Value (Stoich)
15.5 AFR - Lean Cruise
16.5 AFR - Usual Best Economy
18 AFR - Carbureted Lean Burn Limit
22+ AFR - EEC / EFI Lean Burn Limit