3.2 to 3.4 - Does dme box need to be changed?

[brp914]

In going from stock 3.2 to 3.4 with 98mm 9.8 CR Mahles, does the DME box need to be reprogrammed? I guess a related question is whether this 6% displacement bump is beyond the range of the dme closed loop correction. Also, do the tuners known on this board have a good solution?

[Joe Bob]

I would consider talking to Steve Wong and getting a new chip flashed.

[Flat6pac]

The 3.2 and the 3.6 use the same air flow sensor but different injectors so I would include the 3.6 injectors as part of the increase so the chip would be able to take all things into account. Might even increase the throttle body size.
Bruce

[Dave Colangelo]

Having done lots of ECU work on many different cars here are some things to remember. If they 2 engines use different injectors, get a multi meter on them and make sure they have the same impedance. If they dont the system will not work correctly. Most of these things are standard so they may have changed injectors for shape reasons how ever you never know. That being said much of the ECU work I have done is with the reprogrammable MegaSquirt and the like there of. These ECU's allow one to select parameters that stock ECU's dont. In theory they all do the same thing but in practice they can be very different. You also have to make sure they used the same crank sensor wheel. Although the sensors may be the same the wheel's may have a differing amount of teeth which can create an issue. The tooth issue may be able to be handled by software, steve wong would know. I dont know enough about what is on the "chip" to say that it will solve the problem. The ECU will have to be reprogrammed.

Regards
Dave

[Steve W]

Closed loop is only used at part throttle below 4800 rpm and should only be a fallback for constant cruise and idle corrections for emissions, not for delivering the proper fuel if the mapping is incorrect to start off with. You do need to reprogram the DME for a 3.4 to a) deliver enough fuel for what will be a lean condition on 75% of the conditions, and b) to optimize the power available from your investment. Without reprogramming, you engine will make no more power than a chipped 3.2. With reprogramming, your engine will make as much a 40 hp more in areas over the stock chip programming.

Also, the stock injectors and fuel pressure are more than sufficient for a 3.4 and even a 3.5 and you do not need to waste time and money on alternate injectors. In fact the 3.6 injectors have about the same flow rate as the ones on the 3.2, just that the 3.6s run at 3.8 bar fuel pressure vs. the 2.5 of the 3.2.

[RSM-M491]

After reading your post, I went through my receipts from the PO of my car, as I remembered seeing something about 98mm set installed. (to the tune of about $3300) Does that mean the car was upgraded to a 3.4, or not necessarily? Sorry, I do not mean to steal your thread!

It appears he also put in new rod bolt/nut set, and cylinder stud kit.?


Thanks!

Rod

[Lorenfb]

"I dont know enough about what is on the "chip" to say that it will solve the problem.
The ECU will have to be reprogrammed."

Do what?

[Tippy]

Curious Lorenfb, if you do not like aftermarket chips, what does one do in this situation? Proportionately bigger injectors?

[hcoles]

My buddy near here is running a 3.4 conversion with SW chip, all is good. He is using the original DME box.