gcthree

Just had my PFC tuned by Steve Kan. Great guy, a real talent and resource- I highly recommend him.

Peak HP for my car was 280hp, which Steve felt was at least 30-40hp too low given the mods on my car. So, let me throw it open to all the experts out there for your opinions- I'm real curious.

Here's what is done to my car:
First off, mine is a 35,000 mile '93 Touring. The motor was streetported by Chris Rogers in Virginia Beach- another individual I highly recommend: honest, fair, and stands behind his work. Chris put the same street port on my motor that he has on his. And his car is a rocket. A very driveable setup with a smooth idle.
The intake/intercooler is a PFS setup coupled to Efini Y-pipe and stock intake elbow. It has an HKS downpipe, an ATR ultra high-flow main cat (3"), and a Racing Beat single 4" outlet cat-back system. I have a high capacity pump in the tank and 1300cc secondary injectors. I have a Fluidyne radiator. I running NGK Iridium plugs (#10 heat range) with new plugs wires. And a PFC with commander. I run the car on straight 100 octane unleaded fuel. The motor has about 1,800 miles on it since the rebuild.

I'm told it should produce 310-320 rwhp at 12 lbs. of boost- mine made 269 at this setting, and 279 at 14 lbs. of boost (on my guage).

Analysis:
Steve Kan feels there is some sort of 'restriction' on the car: downpipe, cat, or cat-back. Why? First, is the lower HP number, but also that the HP curve doesn't lift as much as it should as boost is increased. The A/F ratios are around 10.5. His suspicion is the donwpipe and cat-back.

Information:
The high flow cat is 6 months old, with not many miles on it- it's not plugged. The plugs were clean, wires new, fuel filter/oil filters changed, the air filter was cleaned and re-oiled. The only issue during the entire dyno session (which went flawless, unlike many cars that Steve tunes) was an idle that 'hunted' a bit. A little tweaking on the idle screw settled it in.

My thoughts:
I talked to the guys guys at Racing Beat about their exhaust being restrictive, and they sort of chuckled. I have bought a mandrel bent downpipe from ATR (www.atrperformance.com) to replace the HKS (which I believe might be a bit restrictive), but nothing in my mind adds up to a 30 hp deficit.

What do you think?

adam c

iTrader: (2)

I suspect the cat is the problem. A DP with a different design is not going to change much. It's possible that you got a bad CB, but not likely.

Check your intake to make sure nothing is wrong.

93BlackFD

get rid of cats, ditch the racing beat, try again

RX794

Bet any $ it's the cat, cats are a hindrance when it comes to rotaries, they clog, stop flow, etc. Take the cats off permanently and you'll see the difference, and never have that problem again.

XSTransAm

possible reasons:
1 your boost gauge is off... ive personally seen gauges read as much as 3 psi high
2 your plugs are too cold for your setup. get some 9's in there.
3 You are WAY too rich at 10.5afr, esp with teh 100 octane
4 timing is key, what is your timing?

clayne

Nothing at all wrong with the Racing Beat.

Throw a mid-pipe on it, have Steve tune it with the mid-pipe and see the difference.

If you see a 50 HP difference, you know where the problem was.

XSTransAm

its not the cat... im sure it will free up some hp... but going from teh stock cat (a heavily clogged one) to a straight through 3 inch midpipe i only saw a gain of 20 hp.

He needs to check his gauge, put in warmer plugs check teh timing and lean the bitch out.

that and the 100 octane is hurting his hp running that rich.

clayne

XST,

I'm sure Steve corroborated the MAP output with the boost gauge before trusting the gauge in the first place. Even then I'm sure he just worked off of MAP anyways.

Also, octane is resistance to burn.

XSTransAm

yeah i dont know what steve uses, but your probably right about him checking the boost. point is tho his highflow 3" cat is in no way possible holding back 50hp unless he has a baseball stuck in it.

clayne

Yea I doubt it is 50HP as well. Posted it as exaggeration.

Well we all know the grim reaper style:

COMPRESSION TEST.

XSTransAm

Jason

iTrader: (5)

To me it sounds like timing unless that cat is really clogged or it could be a combo of both. Do you always use 100 octane?

Jason

gcthree

Hey, thanks for all the thinking!

The cat is no more than 6 months old, with minimal mileage. So, no way it's clogged.

I'll try to shorten the story. I cracked an apex seal, and brought the car to Chris Rogers for a rebuild and street port. I needed a rotor housing, but there were a couple of nicks on the rotor near the apex seal groove, but Chris was absolutely confident that they could be cleaned-up, and the rotor saved. He checked clearances, and seal movement, and it all checked.

Jason, you might recall this story from here- once I had sufficient mileage on the motor rebuild, I brought the car to KDR for a tune. Dave checked compression and told me that I had a stuck apex seal, the front rotor had an excessive variation between chambers, and he wouldn't be responsible for a blown engine if he put it on the dyno and ran it up. I told him to button it up, but before he did, he dropped a map in (no charge!), and I drove it home. It ran like crap! I sent the PFC back to Jason to drop in a map that would enable the car to run, and then returned the car to Chris Rogers.

Once at Chris', he checked the compression more than a half-dozen times, and each time the variance between chambers was well within factory spec. He even called around to other builders to seek their opinion, and the most telling was Roger Mandeville's motor builder (from IMSA racing circles), and he said he'd put the motor in a car and run LeMans with it. We were all satisfied, and the car runs great, except it's not making the HP that Steve Kan feels it should given the mods.

As for the fuel, I run the 100 octane because it's the best anti-deetonation device there is; it won't hamper performance as some suggest.

As for heat range on the plugs, the car ran 'uneven' on the stock heat range plugs, and once the 10's were in, it noticeably improved the driveability of the car: linear acceleration, smooth idle, runs clean to red line.

clayne

100 octane (leaded), but with a cat (high flow or not, it's still a cat)?

gcthree

No, the 100 octane is unleaded. Only $5.49 a gallon! Fine with a cat.

They also have 110 octane leaded for $6.49/gallon. I run this stuff in my 125cc shifter kart. Such a deal!

gcthree

I'd love to lose the cat, but we have a sniffer test during inspection here in NY- no way it would pass- we sneaked it through this year. So, if I have to have a cat, it has to be a hi-flow (3") unit. I'm told the variance between a hi-flow and midpipe is less than 10 hp.

RX7Wishing

Chris is a good guy, he is going to be building my motor for me as well. I live in Virginia beach so i have personaly met him. A+Guy

skunks

install a cut out to bypass cat

93BlackFD

the stock cat IS a high flow cat, i had an ntech hi flow on my car for about 50miles, it was a waste of money, i took it off

don't let marketing terms fool you

911GT2

No one thinks the funky bend in the HKS dp could have anything to do with this?

RX794

I live here in NY also GCthree, I can hook you up with an inspection every year if you want, all the people here in NY with RX7's that I know(and that's ALOT of people), don't have cats, they're a waste of $, and troublesome, I had a cat clog on me in a matter of 3months on my first FD, I learned my lesson after that.

gcthree

Well, I need to know about that inspection station. A midpipe is clearly the way to go, but as I said, it barely squeaked by last year. Can you PM me with the location/person?

I feel that the HKS might be an issue. It does an immediate hard bend down, and the exhaust flow (my speculation) might reverberate back. Chris Rogers suggested that I get a mandrel-bent DP with a better radius, and I've ordered an ATR pipe that should arrive next week. We'll see.

As for Chris, you will be very happy with his work, and more importantly, the quicker turn-around on your motor. That's especially poignant to those guys whose cars have had permanent residence at places like KDR. Chris works on your car, and your car only. And he is always there afterwards to support his work. He's experienced, and great!

mark57

I doubt it's the HKS cat-back causing you the grief. You may want to try a resonated MP ~ unfortunately, the Pettit RMP didn't quiet things down as much as I'd hoped. The GReddy Evo that replaced my worn PFS is even louder; I was chasing after the mellow tone for idling about. Still seeking it.

I cannot add to the solution to what your problems might be; that's been pretty well covered. However, do you have enough fire? Have ya got an ignition amp? Have you ditched the stock lead coil and gone with a bad-*** twin single coil setup? 100 octane is hard to light up and the colder plugs........

......just another base to cover, that is, after you know the engine to be 100%.

mad_7tist

i think 10's and 100 oct is a bad mix. 10.5 seems kind o rich. you would have to drive angry all the time to keep the plugs warm enough to clean themselves. pull one and look at it. what are your intake air temps? Compression. just because it's new doesn't mean it's right

pluto

Nah, the car was actually tuned to about 10.7-10.8: I leaned it out to as much as 11.1 and didn't notice any gain in hp so I richen it back for extra safety margin. why run it leaner if there're no performance gain?

His problem isn't running rich (hp and torque curve was smooth). Something is restricting his air flow (intake or exhaust).