Tuning MAFT w/High Compression

[tanner261]

I did some tuning last night with the new MAFT on my 1G AWD. Relevant mods:

9:1 Ross Pistons
Stock Head
16G w/34mm flapper, 29mm hole
2.5” Turbo Back Exhaust
2G O2 housing w/divider removed
BR FMIC
3” Fender Mounted Intake w/9” K+N
1G BOV w/MAC valve
600cc injectors
-06 fuel line
Spoolinup AFPR @ 44 psi
SAFC
Ramchargers MAFT w/blow through 3” MAS
TMO Stage III EPROM

The car was tuned well at 11:1 A/F ratio with a hacked 1G MAS. Looking at old dataloggs, my IPW would have a spike as soon as full boost hit, now with the MAFT the IPW is a lot more linear and follows airflow well. I’m very happy with the improved driveability with this MAS.

I started with my base timing at 5 degrees advanced, and by the end of the night I was at 3 degrees retarded to avoid knock. At 5 degrees advance there was a solid 30 knock counts, at 3 degrees retarded there were occasional spikes of 5-7, but the ECU advances timing like normal. When applying the throttle slowly there is no knock and timing looks normal as well. I was setting the timing by unclipping the injectors and cranking the engine with the starter. The timing belt cover is off a JDM engine, so I have no Idea if the timing marks are correct with my US crank pulley, CAS, etc. I really don’t see why it would be different, but just in case.

Tuning is being done with a TMO logger and an ETAS wide band O2 meter. My O2’s throughout the pull stay right between 11.5:1 and 11.2:1 on pump gas and 18 psi. Before the MAFT I had solved my boost creep issues through porting the turbine housing and was able to hold as low as 16 psi on the internally gated 16G. After the MAFT, it now creeps from 16 to 18 psi, so I set the boost at 18 and it holds solid through 3rd gear. If I shift into 4th after pulling all of 3rd gear, boost will go right to 20 psi and stay there. If I ease into the throttle in 4th, boost will hold at 18 psi. The turbo spool is simply amazing, full boost below 3k RPM. I’ll also get full boost below 50% throttle anywhere above 3500 RPM. The turbo noise is two times as loud now. By freeing up the intake so much, I now have boost holding issues. It was around 50 degrees outside last night which didn’t help any.

Compression as of last night is as follows:

187 187 185 187

I measured all volumes when I built this motor and it is just barely below 9:1.

The car pulls strong with very little knock, O2’s look good, timing starts in the high teens and climbs to the low 20’s by 7k RPM. I do not have an EGT gauge on the car at this time. High EGTs are my concern when backing off the timing this much, so my next step is to put the EGT probe back in the manifold. I tried to do this last night but the brass plug I used is now stripped and stuck in the manifold. Yeah, I know brass is the wrong material, now I get to remove the manifold to cut the plug out.

I have no concerns with my fuel delivery. Part throttle driving, tip-in, and WOT fueling look great. My concern is with the high compression, high boost, pump gas, and timing. Am I going the wrong direction by trying to run this much boost, compression, and pump gas by backing off the base timing? I’ve come to the conclusion that I need an external WG if I want to run less boost, should this be my next mod? If my EGTs stay below 900*C am I OK with –3 degrees of base timing? Should I not be concerned and just run the car with what it seems to want?

This doesn't make a whole lot of sense to me that the car was running decent with the 1G MAS and 5 degree base timing, but requires less timing with the MAFT to avoid knock. More airflow?

 

[kpt4321]

Try richening it up a little bit, and see if you can add some more timing asdvance back in if the A/F ratio is closer to 10 or 10.5

Keep in mind that, in terms of power output, timing advance is much more important than A/F ratio. You can sacrafice some fuel iun order to get better timing, and gain power.

Are you sure that the gas you have is ok? Sometimes you can get a bad tank....

That's all I can think of right now, but you're right, to have to pull timing that much doesn't seem ok to me.

....Kyle T.
93 TSi AWD "TURBO4"
14b - 12.8 @ 108

 

[tanner261]

I can't say if the gas is all that great, but I'd consider running 10:1 too rich for where I want to be. The fuel is 93 octane from the local BP.

I'd like to get some opinions on what people are running for base timing, boost pressure, and fuel octane with 9:1 engines. Is anyone running less than 0 degrees base timing? My car does not feel sluggish with -3 degree base as some would think. The old 7.8:1 engine did feel sluggish at 0 degree base; it also had a metal headgasket further reducing the compression ratio.

One comparison I have made is Andre's (dre99gsx) car running an AEM EMS using a flat 10 degree timing curve for his latest dyno pulls on pump gas (448whp). I understand that the comparison can't be made between the AEM and the factory ECU, but it seems he is not running very much timing. I'd be interested to know what his base timing is, and if his base timing is already added into the timing maps he's quoted.

 

[NDgsx]

With the stock timing maps and 9:1 compression you're going to need to run a bit lower boost, more like 16psi.
I've tuned quite a few 16G/big 16ged cars with 7.8:1 and without altering timing I couldn't get over 18psi without running the car pig rich (no wideband to go off, but the black cloud is always a good indication ).
With the higher static compression you'll see the same combustion chamber pressures at a lower pressure ratio/flow rate, ie less boost.

Of course you can always get an itc and just pull back timing at WOT, my friend Matt has been doing that with good succes.

I've never been a big fan of pulling back base timing, but I never deal with anything over 8.5:1 on the stock ecu.

 

[Tallen]

richen up MID alot more

 

[jérôme]

i have a similar setup (maft, 180psi compression... -big 16g coming...) and find that i had to retard base timing like you did- my motor is jdm as well, maybe the markings ARE off- i don't know. but my experience is that running the stock base requires a lot more fuel- almost impossible to get rid of knock, while retarding base a couple degrees helps a lot with "normal" fuel settings. is this bad? im worried now because i know ill have to run 17psi or more when i install the 2.5 turbo back and 16g for boost creep reasons. So i guess im just wondering how a lower base timing makes things dangerous for the motor?
also, tanner, are you saying the maf made creep worse?