MicroSquirt.com read only forum (Jan.15,2018)

Hey guys, heres the setup - stock 95 Cobra 5.0 longblock, DIY intercooled kit with MasterPower 60-1 .70/.81 p-trim, home depot style MBC, Tial 38mm WG, Tial 50mm BOV, and 3.5" OPEN downpipe, MSD6AL. Running MSnS-E 024s9

The guy who built the kit said with his stock computer in boost he was seeing 10psi by 3200RPMs......I am not seeing 10psi until about 4200RPMs. My A/F is a safe 11.0:1. I am thinking my timing curve it too conservative and causing it to spool up much slower.

I pull great vacuum at idle and decellaration, the same I did when the car was stock. So I don't think I have a vacuum leak. And I can't hear any significant exhaust leaks at the crossover or anywhere else....

Even if I downshift and stay about 4000rpm and punch it, it will still take a second or two to fully spool up. It should be instant with this size turbo. Let me know what you guys think. Here is a pic of the VE table and spark table since I can't export the tune from my old laptop.

I'm not a v8 expert but at 100kpa v8's with short intake runners should run more like 35 degrees of timing at high rpm's....

if i was you i would reduce the boost to abslute minimal i can (or completly disable it if you can) - just jam the wastegate fully open.
advance timing at 100kpa. advance 2-3 degrees at the time (the whole rpm range) and watch for detonation. I think you should be running more like 32-35deg from 3krpm onwards @ 100 kpa. then reduce 1 degree per 3 psi of boost....

slow spoolup could be caused by other things aswell:
1. wastegate might not be closing properly
2. you are using weak spring on the wastegate (like 5 lbs) and using bleed-type boost controller to force the boost to 10 lbs... that can actually slow up spoolup. It will look like it's reaching 5 psi quick but it takes long time to go from 5 to 10 psi. I'd just for for your target boost wastegate spring, say 12lbs ?
3. bad design exhaust manifold can severly reduce turbo performance.

[edit]
just had another look. timing at low rpm's (500, 1100rpm) should be more like 10-20 deg across all load sites...
Admitely your timing table is stuffed basically. search forums, i reckon you should be able to adapt any v8 timing table found on those forums...


better wait for advice from somebody who dealt with turbo v8's...

mops wrote:I'm not a v8 expert but at 100kpa v8's with short intake runners should run more like 35 degrees of timing at high rpm's....

if i was you i would reduce the boost to abslute minimal i can (or completly disable it if you can) - just jam the wastegate fully open.
advance timing at 100kpa. advance 2-3 degrees at the time (the whole rpm range) and watch for detonation. I think you should be running more like 32-35deg from 3krpm onwards @ 100 kpa. then reduce 1 degree per 3 psi of boost....

slow spoolup could be caused by other things aswell:
1. wastegate might not be closing properly
2. you are using weak spring on the wastegate (like 5 lbs) and using bleed-type boost controller to force the boost to 10 lbs... that can actually slow up spoolup. It will look like it's reaching 5 psi quick but it takes long time to go from 5 to 10 psi. I'd just for for your target boost wastegate spring, say 12lbs ?
3. bad design exhaust manifold can severly reduce turbo performance.

[edit]
just had another look. timing at low rpm's (500, 1100rpm) should be more like 10-20 deg across all load sites...
Admitely your timing table is stuffed basically. search forums, i reckon you should be able to adapt any v8 timing table found on those forums...


better wait for advice from somebody who dealt with turbo v8's...

Thanks for the info.....a few things that you mentioned -

2. The spring in the WG is 7-8psi spring. It doesn't go any faster from 0-7 than it does from 7-10.


Another thing is that the guy that built the kit said he got full boost just above 3000rpms. I have not changed anything physically from the kit from when he ran it, other than the tune since I'm using megasquirt and he was using a tweecer.

different cams will also affect turbo response.
anyway out timing table doesnt look right, so first you need to sort it out. goto to tuning manual (for ms2) there's a sample v8 timing table there.... it's for non turbo, so just adapt it for your uses...

Well the guy that I based my chart off of (very similar setup) said he hits 10lbs at 3100rpm, so I must have a leak somewhere....

cuda6pak wrote:Well the guy that I based my chart off of (very similar setup) said he hits 10lbs at 3100rpm, so I must have a leak somewhere....

do a boost leak test,
then get your a/f closer to 12.5:1 around 0 psi to about 3psi

then get to a dyno and start bumping the timing up until you stop making anymore tq



Richie

Are you sure you have the tial hooked up to the MBC correctly.

What spring are you using....... is you a 0.8 bar spring. (~11psi)

I would disconnect the MBC totally for now and see if the wastegate stays shut.

The spring will hold it solid.

P.S You are running similar timing at boost that I am running on my 2.5L 4cyl just for comparison....

ae1969 wrote:Are you sure you have the tial hooked up to the MBC correctly.

What spring are you using....... is you a 0.8 bar spring. (~11psi)

I would disconnect the MBC totally for now and see if the wastegate stays shut.

The spring will hold it solid.

P.S You are running similar timing at boost that I am running on my 2.5L 4cyl just for comparison....

Yes the MBC is hooked up correctly, the spring is a 7-8psi spring.

238ur50 wrote:

cuda6pak wrote:Well the guy that I based my chart off of (very similar setup) said he hits 10lbs at 3100rpm, so I must have a leak somewhere....

do a boost leak test,
then get your a/f closer to 12.5:1 around 0 psi to about 3psi

then get to a dyno and start bumping the timing up until you stop making anymore tq



Richie

Wouldn't a boost leak cause the boost to drop once it hits full boost? Mine hits full boost fine and holds it, just takes longer than it should to get there.

Boost leak on a MAP driven car would show exactly what you are experiencing...... Check for tears on connectors etc.

At the higher RPMS it will easily be able maintain a boost level of 10 psi. If you were running something nutty like 30.... you may notice it falling off.

The other possibility is the exhaust side leak. THe only way to check those is to get under there....