ScionFred

iTrader: (1)

I'm running a draw-thru maf setup and have some specific tune issues which I suspect are related to the draw-thru maf. Whenever I floor it at low rpm the engine bogs, the UEGO reads lean (---) then the afr goes normal and it takes off. If I power-brake to build rpms and spool, it launches fine. This might not affect MT cars as much but I'm auto and sometimes I just want to floor it from idle without power-braking.

Is this common to draw-thru mafs because of the very greatly increased volume of post-maf air and restrictions contained in the ~6' of piping, IC and the comp housing? Not to mention the spinning comp wheel between the maf and TB. Can it be completely tuned out with an FIC or should I convert to a blow-thru maf? TIA.

cburglb34

when i was draw thru i had some issues like that, but that was on safc, u might just need to smoothen the open loop transition, send me your map ill take a look

m6ar2cel6oTC

It's your tune not the maf setup!!

3min3m2

Assuming you have no leaks, the pressure(at idle) near your MAF and TB should be very similar. so when you crack the throttle, it should register at MAF right then.

I have the UEGO in my NA tc (turbo kit is arriving soon) and when I hit the throttle from idle, It goes to rich side(13ish) then comes back around 14.

ScionFred

iTrader: (1)

Thanks, Martin. I'll be happy to send you a copy of my tune but I really don't know how to force the ECU into OL any faster. If the ECU would enter OL the instant it sees WOT on the TPS, I wouldn't have this problem. Instead, it seems that the vacuum pump (engine) is able to draw a larger volume of air before the ECU sees and reacts to the slow MAF sensor registering the event.


If that were the case, why would anyone bother with a blow-thru maf setup and it's inherent disadvantages?

Two points. First, my NA setup performed similary to yours when the distance between maf and TB was ~14" x 2.75" ID and the volume of post-maf air was very small.

Second, not only has the volume of post-maf metered air increased 10X with my turbo setup, I also have new restrictions between the MAF and TB such as the IC and compressor. IMO, it absolutely takes longer for a pressure change at the TB to be seen at the MAF. The question is, can this be tuned out with a piggyback like the FIC or is it preferable to reduce the post-maf metered air volume and remove the aforementioned restrictions by placing the MAF closer to the TB?

rhythmnsmoke

From what I have gathered is that the closer the MAF is to the throttle body, the throttle response is greater and performance is greater. Thus Blow-thru > Draw-thru. It can still work and work well on the Draw-thru if you have the proper tune though, just keep that in mind. So, let someone take a look see at that FIC map and see if your current setup can't be more optimized.

ElevationTC

What you need is adjustments to the map.

This is why we have a full scale map input/output map.. Its not only ment to clamp the maf or they would of done it much different.

Also what does your o2 map look like?

Post your tune in the form of a zip file on here so we can take a look.

3min3m2

^ 2nd.

I was trying to throw some logic in there...but your makes sense as well!

m6ar2cel6oTC

thats right! but also you would need major adjustments to your map! regardless or blow thru and draw thru! making power and having a good DD is all in the tune. assuming no mechanical problems.

ScionFred

iTrader: (1)

Hey guys, thanks for all your help. I haven't had much luck tuning out my laggy off idle WOT response and was concerned that it might be an inherent problem with draw-thru MAF setups. If you guys say it can be done, I believe it can be. I've been considering a trip to P-Tuning but I didn't want to pay for a tune only to discover that I still needed to convert to a blow-thru maf to get the throttle response I'm looking for.

If anyone is willing to take a look at my crappy tune, I'd appreciate it. My tuning skillz are weak.

ElevationTC

OK, First look at this tune i can see alot of issues!

One timing: your timing is over pulled! Ive seen these cars at wot run around 19-22 degrees of base timing.

I would need to datalog ur car to know this..

Maf map. Your not even letting the car ever see OEM wot maf readings!

and the o2 map is not really setup. Just highlighted and pasted some numbers in!

I can do a quick edit as to what i think should improve things. But this could be extreamly far off since ive never seen your car! But looking at this you can get an idea of were your off!

Give me a few min and ill post something up!

ElevationTC

OK,

I made some changes for you to work off of!

These changes may not work great for your car untill you adjust them correctly! But this is a start in the right direction!

Upload it and datalog it and start making correction from there!

Let me know if its seem more resposive!

**DISCLAIMER** do not download this map thinking it a tuned basemap from me.. I created this soley to point him in the right direction. Its not my map. Ive never put this on a running car. I have no clue what it will do! But again.. this is a example of what he should start with!***

ScionFred

iTrader: (1)

Thanks for taking the time to look my tune over and for sending me a test base map.

Just FYI but the MAF map is closer than it may look to a TC guy. My MAF tube is 2.75" ID vs 2.5" ID for a TC. I logged my oem NA setup and created that MAF map according to AEM's instructions. The highest MAF voltage recorded during a 0-100mph WOT run was 3.8V and the rest of my clamps are set 5% higher than the max logged values.

I'll let you know how it works out. Thanks again.