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YOUR RESEARCHGT3 Cup exhaust and cat delete
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Run standard 3.6
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I run a standard 3.6 using the 1999 5.2 DME and electronically trigger the VC+ solenoids at a preset RPM.
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And it was rushed so we didn't have the correct chin spoiler to put on so ran without.
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The good news is I had set my weight based on 255 rwhp.
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Performed · outcome unconfirmed · Original poster
We used GT3 shrouds to feed the rads so the forward side vents are active.
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Suggestion · Original poster
I would have liked to have given you all an individual breakdown of what each change contributed but it would have been too time consuming it was really the combined effect I was after.
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We're thinking about approximating this exhaust using SS Burns' muffler and pipes instead of the shown Ti version.
We'll remap at the same time but what are the likely cat delete/CEL issues?
FWIW I have dual Burns version on my 964 with no CEL/codes.
I thought about doing a similar setup a time or 13...even found a local shop to build it using Burns mufflers. However, I can't justify the investment of a new rear bumper to go with the setup and don't parcitularly care for leaving the stock bumper with nothing in the exhaust cut-outs since my car is primarily a street car with occasional track use.
I think that setup is the best compromise of weight, sound and performance. This is how the Grand-am teams run theirs too.
As for the CEL issues. Most guys who run cat bypass pipes will eventually get a CEL...it may come and go but expect to see it. Some have had good luck with the o2 housing extenders to get rid of the light. Looks like your car is pretty well track oriented anyhow so does it really matter?
Andy
Dave,
I have been catless since the beginning of spring. Only one CEL after a dyno pull. 02 sensors are plugged right into the bungs for the cat bypass pipe.
The reflash if custom can severely change the thresholds for throwing the CEL because of the cats.
BTW: interesting project... Is that a 99 but with a MKII nose that uses MKI light cut outs? Also are your radiator vents functional or are you still exhausting downward?
-Paul
Thx for the cat comments.
The car is a Mk I with GT3 Mk II bumper. We used GT3 shrouds to feed the rads so the forward side vents are active. And when the center rad goes in, the center vent will likewise be active.
I have side lights on the way that should fit, but maybe only after some minor fitment work.
Don't think you need the 3" one though.
They make a 2 1/2" that's only 12" long that would be perfect for the confined space back there.
http://www.burnsstainless.com/cgi-bi...=SM-250-350-12
I wouldn't be surprised if they just mix and exit. Someone needs to stuff a borescope up the tip and see.
I am very interested to see what you come up with.
Borescope. I like the way you think. I know someone who has one too.
But look at the the stock Cup exhaust- if it was divided then a.) I don't think that the tips would be so very close together and b.) there would likely be a seam on the outside no?
Absent the borescope I guess you could just angle a coat hanger in the exhaust tip and if you don't hit something . . .
I have access to both exhausts on the 996 Cup and 997, but probably won't be able to see them myself for a week or two. I will check them both when I can.
Yes, usually there would be some sign of an internal wall or baffle inside, unless it is piped with a perforated pipe internally (unlikely but possible).
Lucky me, guess what I happened to run across after work today ? An '04 996 Cup car !
Ok, so I shoved a borescope up it's tip,actually both tips, and here is what I found.
The first section in the exhaust is actually a honeycomb cat, just like a street cat although it did appear to be a better larger cell/higher flowing cat. One on each side and it can be seen/noticed in your picture. The shiny, first section of the exhaust on each side is the cat section. After that it is a pipe, one on each side, that comes straight out of the cat section and then 90 degree turns for the exit. Now the reason the middle section is rusty/discolored is that the pipes internally are perforated which appears to mix both sides slightly as well as act as a baffle to dampen the sound.
Make sense ? ? ?
I didn't have a camera to take pictures of the borescope display, not so sure how they would have turned out anyway, but I think it's pretty easy to picture from the description above and your previous picture.
After seeing this now I understand why the extreme cost of this exhaust system, it really is 2 cats and a muffler, not just a muffler.
Let me know if you have any other questions, I can check the 997 although I am guessing it will be the same.
Hey kewl- thanks.
And from the original pic on page 1 - there are baby cats in there I just read.
So the question is then if you eliminate the cats, can the left and right sides empty into a common singular muffler or better off are they better being maintained separate- like this design for example:
That is the million dollar question ! And the only way to get an answer is to build both and dyno, or find someone else that has already.
I would speculate some mixing would help although depending on when and how you mix it could also hurt performance. This gets into tuning the exhaust pulses, and also tuning them for a specific gain at a specific RPM range.
Actually...look closely at that design (which is pure sex BTW) and it would appear they do mix the exhaust gasses right before the exit. See where there's a subtle "x" just after the mufflers where it's turning down to exit.
Yes....probably not ideal for my street car though!
anyone know the story behind the buldge in the head pipes prior to the bend. Just slip joints or a stepped design? Lots of crazy cool stuff going on there.
Comparing to muffler delete with stock cats really isn't fair, the cats are the greater restriction. Better to test vs pure open pipes, now if you can beat that then you are onto something. Important to watch how it moves the power curve, more power may sell more pipes but it is not always better. Be sure to dyno well and watch airfuels and hopefully you can adjust as needed to really optimize what you build. - Remember that your motor is just an airpump, more out means your needs for proper air and fuel in changes.
It was fun to open this up and see the underside of my old car. I miss that thing.
I didn't read all the posts so I apologize if I'm repeating what someone else said. When we put straight pipes on my 3.6L X51 we put the pre-cat o2s in the pipe and hung the post-cat sensors in clear air. It worked great but we would get CELs from time to time. Nothing a small piece of electrical tape won�t fix!
I would second the concern about fuel mixture. Whatever changes you make, make sure you put the car on a dyno to make sure you�re not too lean.
We did a ton of testing on the car and in general the less backpressure you have the more HP and torque you will get but as expected it gets higher and higher in the rpm range. With straight pipes my car had no torque under 4500 rpms but screamed from 6000 up.
It did with me- I found seconds at RA. With my 3.8 motor with track cams, headers, no cats, dual Burns race mufflers + mapping 4500 is min target rpm. Some the grunt of the 3.8 is lost but it howls north of there to 7k. Lots of compliments from GT3 owners too- which are always welcome.
We anticipate similar from the 996 project. Custom map is a given with these types of changes- for motor safety as much as power.
You just adjust to the power band. We had some basic data so we were able to try corners in different gears and using different techniques to see what worked best.
David,
What do you have for suspension? Getting the front to stick with that big wing must be a challenge. It also creates a lot of drag. Does the downforce make up for it?
I've only been on track (Road Atlanta) exactly one w/e in the car. And it was rushed so we didn't have the correct chin spoiler to put on so ran without.
First session it felt unbalanced and like the back end wanted to come around. But as the tires warmed they seemed to cover in part the imbalance. My wrench (IMSA/Rolex experienced) who was there made some damper changes and it felt much better. We are running custom valved/sprung Ksports (forgot what Audion19s had said about them) and I think by the end of the first day they were very good. Btw the wrench said its a lot of shock for the money. And I think he thinks they cost a lot more than they do. We'll see if they last.
We need to open the wing up - car had good grip but lacking in top speed I think. Its such early days with the car- and I'm surely no expert, but almost out of the box I've never had so much fun sitting down before. And it only got better from there.
As far as Spec Class is concerned we'll see how it shakes out in '10. Choosing things like Hoosiers and Bilsteins and allowing bolt in cages just doesn't make sense IMO. That said we won't do anything that we can't easily undo to get back to spec- whatever that ends up being. Meantime will start running in NASA, CHIN etc.
David,
You might try running with just a taco wing or no wing to see how it compares. A one degree change in angle on my 997 cup has a meaningful impact on straightline speed and my wing is smaller than yours. I suspect your wing may do more harm than good. It's at least worth testing.
Jim
Interresting. I think I was one of the first to try the k-sports...and I never even got them to fit the car (rears needed to be machined to fit in the control arms). Sounds like they at least got that fixed. My car was stock height with their spring in the front with the adjusters all the way down and no preload on the front springs at all.
Then again...if you re-valved them and re-sprung them you've fixed the biggest issues. The internals are supposed to be nearly the same to the JIC's which are 3X the money...but when I had mine on a shock dyno the curve that they showed in stock form was completely linear and not digressive at all...and the comp / rebound rates were WAY off.
To be fair, my shock guy told me the same thing though...re-valve and re-spring them and they'd be a great option but at that point I was completely fed up and just wanted to be done with the headaches that went along with them. I'm glad to hear they might finally be delivering on what I hoped to initially get out of them.
Andy
I expect that wing will just blow off one day and we'll see how it goes with just the uprights.
Its early days yet- I expect we'll try a lot of different things. There are some other guys here with similar set ups so at least we have the same air-anchor out back.
I was really surprised at the 3.4 its pretty quick compared to other guys with 3.6s. No problem keeping up. Even felt strong compared to the 3.8- not dramatically slower anyway.
I didn't hear to the contrary but I believe the Ksports were a no-issue install and set up. They arrived (as promised) 2-3 weeks after sending them the car specs- not 3-4 months like JIC (even then they were the incorrect ones). So far I would say that they are at least the equal of the JICs on track (based on two different P-cars though). A better drover might say the opposite.
But you can't argue with the service, delivery time or the price. As always YMMV.
Here's a couple of remarkably bad photos of the first prototype. We used less expensive Magnaflows to get the design right but will use Burns for the next set.
They have not been run or dyno'd yet so I can't you anything about them except they are very light and yet solid and stiff. Hope to give them a try next w/e.
Better photos, weight, hp/tq gain/loss to follow.
nice, can't wait to see the results.
For those of us who don't have the center exit cutout in the bumper we could still use a setup like this just turn the tips downward instead of straight out the back.
Yes, custom map is illegal in 996 Spec.
FYI, the shock package for 996 Spec is being changed to JRZ non-remote double adjustables. JRZ is going to be making a specific package for us, springs & all at a decent price. Hoosiers will probably remain spec for 2010, but we're going to be experimenting in Texas with some other tires (probably BFG R1's) to see if we can come up with an alternative that offers decent performance with greater tire life.
Rule changes are currently being debated on 996spec.net
I only heard it over the phone - its got a bark like a Cup car (not surprisingly).
I'm back in town on Weds and on track next w/e at Barber. I'll know a lot more then.
Dyno will have to follow the week after but we can do before and after comparison but note on stock motor and map with aftermarket headers + stock cats (no mufflers) vs. no cats + this exhaust. Will also weigh it.
FWIW- I took the car to a place that does ALMS prep and support and the head mechanic said that whoever made them was a craftsman- so at least they are well built it seems.
Update- sorry more anecdotal (non-empirical) info.
I was at Barber with PBOC last w/e with the car. Aside from a few minor issues and a fuel p/u issue on hard right handers the car ran well. The car spools quickly, revs freely and pulls hard from 4.5k to 7k, so I'd guessi somewhat predictably some tq loss and hp gain. But remember we just instituted a new LWF AND the new exhaust so hard to isolate the perceived effects. Regardless, together they seem to work well.
Also first time since X51 baffle, oil separator, deep sump and new valves installed.
As for sound, in person (not over the phone) the car idles fairly quietly with a lower freq. Tubi-type sound if you know what I mean. I was surprised at how quiet (relatively) it was. My 964 with 3.8 and similar (dual) exhaust is very much louder at idle- I'd guess +5db at least.
At 5-7k the car howls like a cup car. My support took some videos but they awful- I'll upload this w/e. But here are a few snaps fwiw.
Planning on dyno next week so finally some data with stock map. Its running (understandably) rich so a Steve Weiner remap is in the future so I should have a variety of runs to share.
Did you use the Motorsports dual-chamber AOS and if so, any issues making it fit?
FWIW my 99', 3.4 was protested when I weighed 2790 after Qual at a NASA event 2 weeks ago. I dyno'd at 249 with straight pipes, 91 octane, and stock ECU with a lightweight flywheel. They used a 248 Dynojet, smoothing factor of 4. My A/F rates were in the high 12's- low 13's across the range. The National's champion GTS3 996 was also dyno'd right before me turning 255 rwhp and his A/F mixtures were leaner in the mid 14's. Midrange from 4k-6k he had 15 more HP and torque than mine. Regardless I beat him and all the protesting BMW's too....
The good news is I had set my weight based on 255 rwhp. Now I get to drop another 50lbs. and said thanks to all those protesting Beemer driver's. My car weighed 2620 on fumes with all OEM steel and glass...
No issues on the install that I heard of (or paid for). I think I'm circa 2750 with just the rear qtrs in poly with some gas. No idea on my other numbers yet. The 3.8 weighs about the same and makes 270 whp- they feel similar but the 3.8 pulls harder lower down.
Anyway fwiw here are the video links (can't embed for some reason- can someone?); ones too short, the other too long and they both stink. I suspect the guy who shot it was high, but they'll give you an idea on the sound:
http://vimeo.com/7730841
http://vimeo.com/7730618
I wasn't present but I'm told the car just did 284 whp/ 248 tq @ 6800 on Dynojet (on pump gas). AFR was circa. 12.5 and it was still pulling to 6800 apparently. That's with the custom exhaust and Steve Weiner map.
Maybe its all the map but those are the numbers. When I get the logs I'll post.
David this is a 3.4 right? Those are very promising numbers based on just a custom exhaust, flywheel, and a flash. Did you enlarge the valves when you replaced them? That's 35 more HP then mine made with open pipes from OEM headers, and flywheel. Mr Weiner's mapping doesn't appear to be too extreme with those A/F ratios though I'd like to see the entire run. Regardless, that car should scream at 2750....
Yes 3.4. To be clear we also have a LWF but that should not add any hp- just increase "spool up". I forgot- we do also have some eBay specials on there for headers. They looked good and we cleaned them up slightly but doubt they add too much- if anything just a drop in weight- MAYBE slight hp gain.
I would have liked to have given you all an individual breakdown of what each change contributed but it would have been too time consuming it was really the combined effect I was after. Sorry.
p.s. Note I've taken the "Spec" out of my signature.
Possibly. I tried to do things that would allow us to easily revert to Spec as needed but I just couldn't stop. Basically I'm an idiot.
Unless "Spec Plus" ( I just made that up) ever evolves I may be relegated to NASA/PBOC.
But notice we also have Spec Boxster in the making. I haven't driven one yet but I'm advised it'll school the 996.
Your adviser needs to get off the pipe. I'm 6 seconds faster than the fastest SB at Willow Springs, 5 seconds faster at Buttonwillow, 7 seconds faster at Cal Speedway, and 5 seconds faster at Laguna. I did race a early Boxster with a 3.4 at Miller and that was comparable......
Hummm...my old 3.4l street car made 248 at the wheels with stock cats and aftermarket mufflers on the car.
I guess dyno numbers can't really be directly compared though as environment, calibration, etc all come into play. Baseline vs. modified numbers for the same car on the same dyno are what should really be evaluated.
You got that right. They have to be placed in the proper context.
I hesitate to evn post them but someone asked. It wasn't the number so much I was looking for but the the right AFR and decent curves. As always YMMV (and probably will).
Have you data logged the AFR's yet. That would show the real results of Mr. Weiner's tune. Chassis dyno's, even with directional fans, can't really emulate what the ECU's doing at 80-100 MPH track conditions....
My 1999 996 made 299 rwhp on the NASA dyno. I run a standard 3.6 using the 1999 5.2 DME and electronically trigger the VC+ solenoids at a preset RPM.
Engine internally is completely stock. These #'s are with x51 manifolds, no cats and a complete aftermarket bolt on exhaust. There was a lot more there w/o the mufflers but that was never dynoed.
FWIW: the 996 is on hold for further development as a track car and I am building a Spec Boxster for this year.
Paul I've read all your reports on your build and applaud you for pioneering the way. Your 299 rwhp is X51 territory. I assume they flashed your DME and that along with the headers & exhaust really opened up your motor. Very impressive...
Agree that the numbers can't be compared for all the reasons you listed above. I'm actually quite happy with the 249 number as it allowed me to drop another 50 lbs. off the car placing me right at the imits of GTS3. I know my car is just as fast down the straight as any of the 996 Specs one of which dyno'd at 266.
Have you printed up your "Fu#k Cancer" sticker or have a sendable file? It would look pretty awesome on the back of my Midnight Blue race car. I think I sent you a PM months ago about my GF who is a survivor and donates endless amounts of time giving makeup and hair seminars to ladies going thru treatments. I would get big bonus points for wearing that sticker on my car....
http://www.janping.com/Jan_Ping/Home.html
