Exhaust - what is everybody doing?

[aeshultz]

Time for some mods to the car - I'm currently running a stock muffler w/cat, which will need to be removed. What is everyone running - keep in mind that my car is street legal and (for the time being) driven to the track. I need some small muffler to keep from attracting any more attention than needed. Suggestions? TIA,

Alan

[944-Spec#94]

I have run well for years using a stock headers, test pipe and a stock muffler.

[aeshultz]

Thanks Joe. I forgot to mention that I've got the stock header (of course). Did you have the test pipe made, or are they available somewhere?

[chris_venturini]

here in the rm region dave dirks is our exhuast guinea pig, he claims 3inch is the way to go.

 

i got under my car and measured the exhaust, i have the california emmissions option code and looks like that means i have a larger cat as well as what looks like a resonator right after that, in between the cat and res the exhaust is only 2 inches and after that its 2.5. i plan on doing a header back exhaust with a hi-flow cat (look into catco or magnaflow for a high flo cat) with a magnaflow race muffler. ill wait for dirks' dyno results before i decide on pipe diameter.

[dmdirks]

here in the rm region dave dirks is our exhuast guinea pig, he claims 3inch is the way to go.

 

I'm not sure if it's THE way to go, but someone else on the forum has had good results on the dyno with 3" pipe on two cars, so based on that it sounds plausible.

 

Anyone else have some dyno results to share from their exhaust systems?

[nhamden]

I am looking for a muffler for my car, it is way to loud for me, I just called Flomaster's technical dept. I told the guy my car has a 3 inch pipe and he said that is way to big, stock is 2 inch and the most I should go is 2 1/4 with the 50 series Delta 2 inch in/out part #942051. I do want the muffler, but I would like to hear from somebody that has dyno'd with different size pipes.

 

Mikael Weitze, were are you? What size pipe are you using and does it make a difference to have your exhaust pipe stop near the front side of your gas tank?

 

Thanks for the help,

[Tim Meyer]

Here's what I found to get the most hp on the dyno:

Stock '88 header, 2.25" to just before torsion tube, 2.50" to flowmaster (2.50" in and out) in stock locattion.

 

I tested 2.25", 2.50", 3.00", no muffler, flowmaster, stock, cherry bomb, turbo mufflers.

 

Exhaust sizing matters because you need to ensure proper velocity to exit the system. If the exhaust is too large, then you don't get proper exit velocity and you don't scavenge the exhaust properly. I did see 2-3 more hp without the flowmaster, but was too loud for most tracks and me.

 

Regards.............................Tim Meyer

[nhamden]

Tim,

 

Thanks for the info. and good luck next weekend at CSW. Still looking forward to racing with you sometime soon.

[944 Swede]

Norm, I was told it makes a difference. Never tested anything related to the exhaust on a Dyno though, just been listening to people I trust.

[Spec-944#70]

Why don't you make something Spec? Then there won't be any debate as to what makes more power and who has spent the most time/money on dyno testing. Just a thought!!

[nhamden]

I agree with you Eric, I am not asking for more rule changes, the last time I saw that movie it was longer than "Gone With The Wind" I don't want to sit through that one again!!!!

 

But your post just reminded me, here is one more thing I am making phone calls and getting on the forum to find 1 or 2 more h/p's. That is what I was wanting to get away from in my last race car. Tightening up the rules does make this series alot less stressful, cheaper and a no brainer, just get out and drive as hard and smart as you can and may the best man win. (not machine) About a year ago I spent a couple of hundred dollars on a 3'' pipe, now I may go back to were I started for another couple of hundred dollars, Is that stupid or what?????????????

 

Thanks for the reminder,

[comatb]

Why don't you make something Spec? Then there won't be any debate as to what makes more power and who has spent the most time/money on dyno testing. Just a thought!!

Eric I agree that this sounds good but there are some drawbacks. Would there be only one supplier. If not how do we assure continuity of materials, size and shape. If it is one supplier then the shipping costs accross the continent become a cost factor.

 

Maybe we could spec diameter and wall thickness, but length would be a difficult one to control as bends are not all the same. Just my 0.2 cents worth.

[Spec-944#70]

Norm - This is what I told Tim when the changes were made. NASA should have taken the time to Spec EVERYTHING if they were gonna do it they may as well do it right. It would open up the possibility for more sponsors also, brake pads, sway bars, bushings, exhaust.....

Then all you do is build/change your car to the new rules and everyone is the same. As it is now there are still differences. LSD the biggest and most expensive!! Do they make a difference? You're on page 2 of one of cheapest one now.

As for Specing the actual exhaust it could be fairly easy. Stock all the way; Spec a size pipe and muffler and have it bend the same as stock and exit the same place; or Spec a more racey design.

I agree Norm there is no need to get into the changes again but go through the rules and look at them. Then look at all the cars running around and check out the differences. This class as great as it is; is far from Spec!! Just pointing out a fact and not being a jerk.

[944-Spec#94]

The truth is 944 spec will never be a 100% spec class. Logistically it is nearly impossible and doing so will actualy drive the costs up greatly.

 

 

We drive old cars with no factory support and order to keep costs inline we need to make some compromises.

 

 

On Rennlist Nor-Cal guy posted about his experinece in Spec Miata vs MX-5 Cup (using all new cars). I believe this drives home some of concern about "spec everything" and what benefits and drawbacks come with it.

 

I've only done one Cup race but the differences and similarities are clear.

 

Differences:

1) The fields are tight, far more than SM. I qualified 17th...but was only 0.8 seconds out of 7th...11 cars within 0.8 sec. Even our +65 car SFR region SMT field won't be quite that tight.

 

2) One model year class plus sealing things makes it easier to have cars that are equivalent. Setup and driver are even more important than in "Spec Miata".

 

3) You have more confidence that things are equal so you don't worry about someone walking away from you who didn't out drive you. Obviously it'll never be 100%...but I never got pulled when I thought we exited a corner equally (and I'm in the draft) like what happens in SM sometimes....

 

4) Durability and reliability hasn't been that great with the hardware...tranny and ABS seem to be a common failing point. KONI Challenge teams also have issues with them. With all of this electronic stuff maybe there just are more points of failure. They had hub issues but that appears to have been fixed. I expect them to get the tranny issues solved too.

 

5) 45 minute sprint race is more than 50% harder than a 30 minute sprint race. Going to have to drop the Krispy Kreme and pick up some weights.

 

6) Few used parts, costs are a LOT higher.

 

7) The draft is more important than in SM...or at least it feels that way.

 

They give you money at the end of the race...

 

9) You have an autograph session with umbrella girls standing behind you...

 

Similarities:

1) Hard driving. Fender on fender at times but nothing different that regional and national SM races that I've been in.

 

2) Better driving at the pointy end just as in a SM field. Less foolish passing attempts.

 

3) Aggressive start....just as in SM, we had wrecks on the first lap...at least we got past the first 8 corners though....but 3 wide driving into the first corner and such...same stuff.

 

4) Even with more power it's still a momentum car and you MUST carry the speed. I know where the 1.5 seconds I have to pick up are...I just have to clean some lines up and grow some larger ones.

 

5) We're still the red headed stepchild at the pro weekends. Bookended for practice, qualifying, and race. Qualifying 8:00AM Sat, race 4:00PM Sun...that's a wide bookshelf....I see we're bookended at Portland too.

 

 

Overall, I like it better. If SM could be that way it'd be great because of how reliable the cars are, however, the cat is out of the bag and you can't make a multi-model year class work this way.

 

It's also fun to run as a support race for the big boys, although I don't get to spectate as much as I'd like as we're a little busier.

 

I am irritated that there are so many mechanical issues with the new cars and I think it's a shame when someone can't race because of it.

 

Cost is still too prohibitive for a budget racer. I'm not poor, but I can't do a full season so I'm doing 3 races this year. Maybe if I give up SM next year it'll be different...but that's not yet been determined.

 

I wish the fields were larger. We had 28 cars, but I'm used to +60. Many parts of the race I was by myself looking for more to do than hot lapping.

 

Again, it's only been one race. We'll see what I think after a couple of more.

 

Kim Ouye

Rennlister : Wreck Me Otter

[944-Spec#94]

..., here is one more thing I am making phone calls and getting on the forum to find 1 or 2 more h/p's. That is what I was wanting to get away from in my last race car...

 

Norm,

I honestly cannot say how much hp is really out there with the exhaust. Chasing 1-2 hp is really hard since I'd expect day to day dyno variation to be on that order. So test a set-up on monday and them come back to the same dyno on thursday with same set-up I would not be surprised to see a 1-2 hp difference. Maybe you could see real change if you took alot averages and really watched the cruves closely. I do believe you may be able to see 2 hp with less than 1 hr between runs. Point is I wonder how accurate the information we see posted here is. I am not saying people post false information, but how much is really there vs just appear due to variation and what people want to see. If you really are chasing 1-2 hp it will take alot of dyno time and careful study to confirm much of any thing.

 

In the end I don't believe 1-2 hp is going to make any difference on track. 5-6 hp probably will make a small difference, but 1-2 hp?

 

Norm if you feel your exhaust is too loud you can always go stock. I think I have 2-3 spare stock mufflers complete with pipes.

 

BTW... I also have 2.25 in straight pipe in addition to my stock muffler. I have never dyno tested them nor even completed back to back track test. Maybe I will on 9th? I never really liked the straight pipe since it was so loud in the paddock.

[aeshultz]

Either way - this is good info. Keep it coming, folks.

BTW- I put the car on the dyno last night. Four pulls, all between 112-113 rwhp.

Looks like I've got a bit of work to do, huh?

At least now I have a small excuse! (Bill knows what I mean).

 

Alan

[944-Spec#94]

Either way - this is good info. Keep it coming, folks.

BTW- I put the car on the dyno last night. Four pulls, all between 112-113 rwhp.

Looks like I've got a bit of work to do, huh?

At least now I have a small excuse! (Bill knows what I mean).

 

Alan

 

Were those pulls on a dyno jet?

[Spec-944#70]

Joe you are partialy right but comparing a single model car class to ours is irrelevent. We have 3 basic models 924S, 83-87 944 and the 88's. When NASA decided on the changes they should have gone a bit further to make the cars Spec and it would not have raised the cost. In fact it would have lowered it. Yes some more cars would have had to spend money to meet the new rules but that allready effected quite a few drivers. You will still have guys chasing every last bit of HP avail any way you go unless everything is Spec'd out. You said you don't think there is HP to be found (maybe 1-2 HP) but you also said headers were a waste as they didn't provide much either. You were wrong about that so maybe with some creative engineering someone will find some HP with intake, and exhaust combo's. My point is people will always look to build a better mousetrap and still be 100% legal. Then NASA will say it's not in the "Spirit" or "intent" and make them illegal.

You need to lock it down now before you have issues again like you just went through. One thing to notice is the Cup guys are not argueing about issues with thier rules. They allow the tweakiing racers like to do and have compensated for it and their class is growing back east. We would have been much better off to join their class with our cars and get assed a weight handicap.

[944-Spec#94]

One thing to notice is the Cup guys are not argueing about issues with thier rules. ...

 

We would have been much better off to join their class with our cars and get assed a weight handicap.

 

Eric,

Really the number of people complaining about rules are really only 5-6. They are all POC guys with cars modded beyond the current rules. Many of them have deciede to just run POC. Sure there are some guys not overjoyed with back dating a few items, but the realize that is it good in the end.

 

I really feel like you are out here to poke hole in everything we do. Tighten the rules and you complain they are too tight. Don't make changes and complain the specs are too loose. Then offer that we need to open the spec further. I really don't know how to please you. Frankly I am done trying.

 

944 spec is not a perferct class. It never will be the changes NASA made this year were for the better. Infact there was a revision that spec'ed exhaust to end. Due to all the complaining we just went with headers. Compromise? Yes it was. I do think it was a fair compromise however and the rules for the class have never been better. It seems that POC rules and NASA rules will diverge. So why not just make POC's class your perfect spec class like you want. If it works well there maybe in a few years NASA can consider that. Until then I suggest we work with what we have. It may not be 100% perfect, but this class has always been about get 90% of the way there for 20% of the cost/effort.

 

We could in theory spec each any every part on the cars, but effort for drivers, builders and post race tech would be well beyond what we are looking for. In the end while close cost effective racing is the stated goal the real measure of the series is how much fun drivers are having. I for one have been having alot of fun and can't find any racing series locally where I could have more fun at any price. Then again maybe all the fun is just from racing and hanging out with guys like Glenn, Norm, Jon, Vince, Steve (both of them), and all the rest of crew.

 

Those of you that missed the fun at the night enduro you missed alot. Just whating Glenn scavenging for old used up throw away tires around Bryan's Toyo trailer, then strap on 2 KC daylights on bumper from his wrecked red car only to to direct wire the light to the battery was just classic. I can't thing of any place to have more fun.

 

Oh... the racing was pretty darn good too.

[aeshultz]

Yes, Joe- those are DynoJet numbers. I don't have the file with me right now, or I'd post it. We did four pulls just to make sure- I've got the NASA GTS certificate also.

Now - where do I start - but that's another post.

Alan

[Spec-944#70]

Joe first of all get your facts straight. I never complained about the old rules and have always been a proponent to Spec the rules up. Ask TC as I brought this up years ago when I joined and also when the recent rule change came about. My complaint was how it happened and when. Not the fact NASA is tightening up the rules. The new changes were also done against the majority on the BB. Yes you tightened up a few areas and "cost" was the biggest influence and also to "try" and equalize the cars. This is all good stuff but you didn't take it far enough. The biggest cost next to a rebuild is an LSD and most of your current builders are complaining about the cost of parts to rebuild or go Spec as it is. They will never lay out the $2500-$4000 for a LSD equipt tranny. If you want a Spec class then make it one. As for the POC the rules there are stable and no one is complaining. The POC has more cars showing up and the guys are having fun.

As for the rules changes it was to make the front runners who built 100% legal cars to slow down so those who could not afford the $ be able to keep up. Mike was the only one who back dated his car and is still winning but is also under suspicion of cheating. Now you have an opportunity to tighten up areas that are open to interpretation and you say you're good enough. You are right the rules are not 100% but it won't be long before you'll find a need to tighten things up again. The rules changes that cost guys $ were all for what? 10HP? You have a guy here with 115RWHP. How is he going to keep up? A complete rebuild will get him up there along with some dyno testing.

As for pleasing me Joe I'm not the one you need to worry about. It's the new guys building cars and searching for everything they can get.

As for Specing everything out I sent TC a list and we spoke about it in detail. It's not that hard or cumbersome. Most of the stuff won't cost much especially if the cars were kept stock. Tim can back me up on this. My point was insted of putting a band aid on your rules your should have scheduled surgery and done it all. Think about all the discussions about exhaust, bushings and others that could be avoided.

Don't please me: Please everyone else. Rules that are black and white leave nothing to interpretation and leaves it up to setup and driver skills.

Isn't that your "intent".

[944-Spec#94]

Eric,

I don't really know what your are trying to achieve here. Are you looking to get back in?

 

I can tell you what I am trying to achieve and that is to keep growing the class while staying loyal to its initial intent. I don't have all the answers, but at the same time I really hate to see people "chasing mysterious hp" in an effort to keep up. In the end 1-2 hp is not a big deal. 2-3 hp peak and 10 hp at 4000 RPM is HUGE deal. The 2007 rules chages were a compromise. They were the first big restriction in class since 2003 when we went with spec tire.

 

Frankly I was quite disheartened to learn that we even had to make these changes, but what I came to learn about the possibilites of these parts forced our hand to some degree. I knew it would upset drivers as nobody likes to take things away. Here in Arizona many drivers were surprised since they have run aftermarket headers and tuner chips and been on a very level playing field with stock chip & headers. Most asked my why make the changes, you can see there is no gain. Well my response to them was that it was not them, but other guys in other places who seem to have found something in these parts that nobody else did and that would upset the balance of the racing. Once explained most agreed that it was the right thing to change the rules, but also lamented that it was needed in the first place.

 

So in the end the 07 rules changes were a balance between keeping existing drivers somewhat happy, but also targeting the clear knows that would upset the playing field before the spread. With respect to LSD and 5th gears the reasoning is simple. The cat was let out of bag long ago is it would be extremly messing putting it back in. For stuff like the rest of the exhaust it was felt that spec'ing the entire system would be alot pain to alot of guys. Even then like Bill said what do you spec? Stock sounds nice, but if you think stock headers are hard to fine try stock mufflers. There are out there, but I'd gess 25-50% don't have them any more. Then what do you do. Spec out tubing? Sure can, but what about muffler? Force everyone in to buying brand XYZ's supermuffler? Possible yes, but when asked why is it being done of the answer is to save 1-2hp most folks would laugh.

 

So we figured forget it. Limit the header and be done with it. So maybe with a custom tuned chip, special intake (before the AFM of course), trick headers,and trick exhaust you can get what 5 hp peak and may be 10 hp 4000-4500 rpm? A gain like that is enough to blow other cars out of the water. So take away the chip and the header what do you have left. 2-3 hp peak or maybe 1-2 hp all the way accross the board? Not bad really.

 

What would I be happy with? I would be happy to see all 944 spec cars turn numbers between 132-137 whp. A 5 hp spread for 90% of cars considering they are all using 19-25 year old blocks is amazing in my book. I am not sure how close we are to that, but that I would consider to be "close enough".

 

Now with respect to Aeschutlz's 115 hp motor. It will need work in some way. Not sure what right now, but I can say that a few bolt on here and there are not his magic bullet. My guess is that there is something wrong causing the low hp. Hopefully it something simple and easy to get at, but it could very well be a motor thatn needs a fresh head or new rings. I have seen low hp numbers like that cause by partially bent valves and by old partially busted rings.

[aeshultz]

Hey - didn't mean to start all of this- really!

For my part, I've got no problem building a car to the rules as written - and I expect to do so to be competitive. If I had wanted a "true spec" class, I'd be racing a Miata. Seriously.

I posted the dyno results to gather suggestions and to illustrate what a weak stock car comes in at. I don't expect to be able to drive up to the grid and be 100% equal to everyone without doing some work. Hell, I can't see cars ever being 100% equal in any case (SM case in point).

So let's not beat beat each other up over this stuff - if it doesn't suit you, race somewhere else, or start your own series. You can ask Joe how much work that takes.

Alan

[944-Spec#94]

Alan,

You are not at fault at this at all.

 

For some reason your motor is well below stock hp levels. I believe stock cars in good working order should put out mid 120 hp levels on a dyno jet. This is with a cat. Most of spec cars run without a cat at the low 130 range just from removing the cat. Point is Cat or no you have some issues causing you to be very low. What it will take to get to the spec hp levels are not "performance" upgrades, but repair type work. If you are lucky the repair work will be all external. If not then you may need to rebuild the engine. Sadly I fear that you will need to tear the engine apart to fine the issues. I hope I am wrong.

 

If you do need to rebuild then the following should get you to full spec powerlevels

 

1) stock head work. Make sure the valves seat properly and the head is flat. Nothing facny here just a basic street car motor type repair

 

2) All new seals, gaskets, & bearings.

 

3) clean crap in the engine.

 

4) new rings in the old block of the rings are worn/broken. Don't bore the cylinders as they are not easy to bore. Only stock bore sizes are allowed. I have had great results with original rings as well if they are not failed in the first place.

 

5) Any crank / oil pan work you want to reduce the risk of #2 bearing failure. Crank is otherwise stock.

 

6) replace any worn/broken parts with stock street car type replacements

 

Doing all that should get you to spec type power levels without a cat, but with stock intake, stock muffler, 2.25 dia exhaust and making sure the AFM is adjusted to produce a proper A/F Ratio.

[Spec-944#70]

You didn't start anything. I'm just once again pointing out issues with the current rule/mindset. Even the supposed "monster" engines that were built to the past rules did not acheive much more than the 137RWHP given as your benchmark. And Joe even said 5 HP (if that!!) isn't going to matter that much. I still believe we could put any one of 5-6 drivers in a 125 RWHP car and they would still be on top of the podium. It was always about driver skill. Some just can't admit that. The proof is the front runners before the rule change are still the front runners now.

And I am honestly not trying to just stir things up. It just needs to be understood that racers will always look for more HP or an edge somewhere. Once someone is lucky enough to find something they will be made illegal. Just wait till guys start using Tarret sway bars or something else. People will be screaming foul once again.

Another thing is this is the place to have those discussions. I have kept everything professional/civil and have just expressed my opinions. I hold no ill will to anyone. I have had conversations with Tim and even though we are passionate in opposite directions I still concider him a friend and will gladly sit and have a beer with him. This is not personal. I just feel there are problems rearing their heads and NASA has the opportunity to stop them.