Do you have a aftermarket midpipe? If so, who made it and is it resonated? What kind of gas mileage do you get?

My FD gets about 10 miles to the gallon (tops) and runs pig-rich. In your opinion, is it safe for me to replace my stock midpipe with, say, and RX7 Store resonated one?

My mods:
Pettit Unlimited
DP
PFS catback
Mild streetported rebuild from Karack w/ about 8k
Cut stock intake box ala AdamC
ARC (soon to be Blitz) SMIC


Thanks for any info! I've searched, but there are a TON of threads with "Pettit Unlimited" and "midpipe" in them that have nothing to do with my question, and I've been sifting through them for like a week.

 

Many people run the Pettit ECU with midpipes. I have the RX7 Store midpipe, but I welded in a metallic substrate cat. When I was running the Bonez hi-flo cat, I was getting around 13 mpg with mixed street and highway driving.

The ECU will handle a midpipe without any problems. What you need to make sure is that you can control the boost. Midpipes have a way of letting things get out of control in that area.

 

Thanks, Mr. Links. That's one thing that I forgot to mention. I have NO boost controller at this time. I'm thinking maybe two Hallmans tucked away under the hood...Hidden from the Smog tech, of course.

 

Running a mid pipe should help as it will lean out the fuel abit more w/ the increased airflow. If youi need to pass smog its going to be tough. Need boost control for sure. G

 

I'm running the Pettit ECU with a custom 3" resonated mid-pipe and the gas milage on my car is around 15-16 mpg street/highway driving.
Even with a boost controller and the Pettit ecu my boost spiked and I blew my motor.

I have gone full non-sequential with a ported wastegate and GReddy E-01 EBC now I have no boost issues and the Pettit ECU does a great job if you keep boost under 14 psi .

 

Cool. So it's looking like once I install this boost gauge of mine and buy/install a couple of boost controllers, I can run my midpipe without too much worry.

Thanks for the replies.

 

has pettit ever showed the specs of their fuel map vs the stock map?

i bet the vacuum map is pretty close to the stock one, so fuel MPG shouldn't change much...

 

[QUOTE=Natey;7660358]Cool. So it's looking like once I install this boost gauge of mine and buy/install a couple of boost controllers, I can run my midpipe without too much worry.

I'd still worry, with a free flowing exhaust you can only control the boost so much, it will still spike but this has been covered a thousand times on the forum.
Like I said my car spiked and blew an apex seal and I was using the HKS EVC boost controller.
The Pettit unlimited ECU will max out the fuel injectors at 14 psi of boost which was told to my by one of the Pettit techs. That won't protect you from any spikes in boost.

 

...you'd better worry unless you get your wastegate ported.

Running a MP nearly always allows so much flow that it will overpower the stock wastegate setup. Without porting your wastegate (and even that is no guarantee), you can run as many of the most complicated and expensive boost controllers you can find, and you'll still spike/creep.

 

Look into the SMB midpipe that has the metal cat AND a muffler. Very quiet, top quality construction. Flow is comparable to a resonated midpipe such as RX7 store's. Just a bit less b/c of the cat. The cat helps keep the stink down and adds just enough restriction to help control boost w/o taking as bit a hit in performance as a full size ceramic type cat.

You should maybe consider visiting a dyno shop and do a couple of runs to check exactly what kind of AFR you are running. I get better mileage than that in mixed driving and you are just guessing at whether you are running "pig rich" or not.

 

i'm just bumping this back up because i never got an answer and i'm still considering getting the pettit unlimited, as i plan to stay on the stock twins...

 

No, Pettit has never released the details on their MAP. I'm not sure why they ever would. That would be like Steve Kan posting some PFC maps.

 

Many have run the Pettit Unlimited with completely open exhausts at 15psi boost without any problems. But since it was designed as a one for all ecu, it does run rich. It has been OBSOLETE since 1999 when the PFC came out.

Time for you to join the real world and buy a programable ecu which when tuned will solve all of your problems.

 

I couldn't agree more , but I have to smog this beast, and it's much easier to swap out the ECU then hide the PFC from the Smog ****.


Also for the record, I'm keeping the stock midpipe and cat. My car runs too well to blow it up for a few more HP.

 

I had a Pettit ECU it ran super rich, fowled stock plugs and was to timing advanced (knocked)for my setup (see my sig) when to a PFC… there is no comparison in my car runs clean , fast, fun to own. Bottom-line is once you make 3 or more mods you need a programmable ECU.
I do have question:
What exactly is boost creep? I would appreciate a definition, or some links. Is it a static condition, or does is increase with time, long term, or over a pull?? Thanks

 

pretty much

running the stock injectors with a Pettit ECU is too risky (unless you want to stay at 13 psi or less, also what KK said about the wastegate porting issue)

 

do a search, there are countless threads on the topic...unless you port the wastegate, you most likely will get creep with a mp

 

I did a search, I have read why it happens and how to correct it.... but what is it???? My car boosts to 16 psi relative in Denver. But its consistant, it that boost creep??

 

I posted some links in the other thread you asked:

https://www.rx7club.com/showpost.php...95&postcount=9

 

Hey, I use to have a Pettit Unlimited ECU with full intake, turbo back exhaust with midpipe and pettit downpipe to a greddy catback system, pwr radiator, pulleys, pettit med intercooler, and wires. My boost was at 12psi via MBC, I had no problems with spiking or creep. Gas Mileage was between 16-20 city and highway. When I switched to the PowerFC driveability was better as was my gas mileage and was much more pleased with the PowerFC!