So, my car's at Pettit with Cam, and he's been telling me that the stock ECU does a good job at tuning the car itself, and what my Cobb would do is "turn the fans on earlier". Is there any real benefit to get it retuned by someone else, and honestly should I be worried? =_= I mean I know Pettit themselves are pretty reputable at this but... it sounds kinda fishy when he told me that I really don't have to retune when I get the engine blueprinted and ported.

 

Get it tuned.

Are they flowing your injectors too? That alone should require a retune as it will almost always result in them becoming larger.

My Pettit motor was seeing very rich AFR under cruise loads 10:1. I don't have the porting template nor know exactly how big the Pettit port is but it makes a significant difference.

 

^^If AFR is that rich in closed loop then something is fubar. What you think is cruise may not be closed loop. Generic terms and poor understanding do not a good tuner make. 10:1 only means rich AFR. Your statement is the equivalent of trying to claim that 1 + 1 = 3

In terms of performance the net result is minimal at best. Porting a Renesis yields very little power improvement as compared to the prior rotary engines. Mazda already got most of that for you.

They are likely telling you this because in closed loop the PCM will automatically compensate and as I stated the net change from porting a Renesis is minimal. The factory PCM also is known for very rich AFRs under open loop/WOT conditions so some extra air flow will be easily covered as rich as it tends to run.

In theory porting increases air flow which in turn would mean leaner AFR so if you want to place guessing games a ported engine running excessively rich AFR could just as easily mean that it is performing worse than a factory engine. Of course when you're guessing it makes sense to go ahead and guess what you want to hear or believe instead since a guess is nothing more or less than a guess regardless.



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Sure, the ECU does a "good" job of "tuning" itself through fuel trims and maf readings, but that still doesn't account for the fact that the stock tune is designed to be a "one size fits all" tune where you will see stupid rich AFRs at high loads.

 

4-6K RPM loads of 30-60% that being open loop. With that said I was referring more to the injector flowing then the porting itself.

OP asked about tuning on a petit motor which I have and in the process of tuning. I do agree that it is not a necessity but what is the point in getting porting done if you are going to run the OE tune kinda defeats the purpose IMO

 

Well I suppose that begs the question of how you are determining accurate injector duty load figures, both before and after?

Since Petit has the capability and does indeed do their own tuning via their EFI-Dude relationship it strikes me as ironic that you place so much faith in their porting work yet so little in their advice

 

this
and this
if it were necessary they would do it
with all due respect they know more about the subject than anyone here
their reputation is on the line with every engine they build...I don't think they would chance it

 

but to play devil's advocate I have ran a Pettit built streetported engines against stock/remans and the difference is obvious
despite the driver the Pettit builds consistantly perform better compared cars with identical mods besides the engine
I won't go into further detail as I don't want to derail the thread
anyone wants anymore info PM me

 

comparing a hand-built engine to factory or craptastic reman is like comparing a burlap sack and a silk purse

a well built unported engine should dyno 265-270 hp at the flywheel, good luck getting that with a factory/reman

ported is maybe 5 - 10 hp more tops, to hear other people explain it sounds more like 30+ hp, not gonna happen

 

well said Team
amazing what people on this forum spend to gain 5-10 hp though

 

look at Racing Beat's info on flashes. it looks like there is very little to be gained by the flash
Power Control Module (PCM) Flash - Specifications and Technical Information
maybe that last 5hp or so

 

I have a street ported and the ecu has not done a good job of tunning at all, The car is very rich and at 8k it drops, is like hitting a wall and makes a sudden lost of power. I dont know how to explain, i got a pic of the dyno, I just bought a cobb so i can get it tuned.

Thats the first run, 189hp and the second run...