[williamoss]

I have a 968 that I bought directly from Pete before he went out of business, I am told he is back in business, but I do not know this personably. It has his exhaust on it, with a chip, i think type 1. Does it make any sense to add a tuned header to the car? Does Flash make one to fit a street car?



And also a long time ago and I mean a long time ago I heard the term PORT and POLISHING, which i believe is making the exhaust hole match the size of the header where it mates to the engine so there is no restriction at this point and then polishing the inside of the engine block at this point to allow the flow of gases from any sort of minute resistance. Is this even correct? and is it still done?



William Moss

Tigard OR

1995 968 Coupe

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[flash]

pretty sure ron1688 has an rs barn header for sale

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[Cloud9...68]

As far as porting and polishing, yes, it's still done, but doing it right means either A LOT of very expensive trial and error, or some very sophisticated flow modeling. It's one of those things that can do more harm than good if done incorrectly, which I suspect is what happens most of the time. And even when done correctly, the potential gains on a modern engine are very modest. Plus, the gains may not be uniform - you could for example gain a few horsepower at the top end, but sacrifice at the low end. You might want to contact Lindsey Racing, as they claim to have done a lot of this type of work, but in my opinion, money is better spent elsewhere.

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[williamoss]

So is there any sence in just adding tuned headers, and no port and polishing?



Any other modifications suggested to a street car with an occasssion autocross?

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[94SilverCab]

Headers do add both HP and torque. I will not try to delve into how much because that is always in dispute. If I said 15ish that would be a Rough Order of Magnitude estimate.



Jay

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[flash]

that is really too broad of a statement. they CAN add power, depending on the design. there is no free lunch though. all by themselves, one type will give you more bottom, and one will give you more top, each at the expense of the other.



there have never been any charts published showing any 968 header, all by itself, showing any across the board gains. in fact, i don't think there are any charts out there showing just the header all by itself, with no other additional mods. the charts out there that show the header also have a cold air intake and i think also a chip in the mix. no 4 cylinder header will add 15hp. you may see 7 or so. even V8s have a hard time gaining 15.



that being said, some headers work well with other mods.



the rule of thumb is try-y for low end and 4 into 1 for top end.



the real issue though is what happens after that. too much increase in flow costs low end torque. it can also mess with the mixture, and cost you power.



there are a few good sources for information on this. burns is a good one, and pretty much the industry standard.

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[94SilverCab]

Yup, like I said...Order of magnitude; more than 1.5 HP and Less than 150 HP...



Jay

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[flash]

lol - one of these days, somebody might just put on a set and take the car to the dyno, and test it with no other mods. i think the results might surprise some people. my tests, which admittedly were associated to something else, of the 4 to 1 header many are using, showed almost exactly what i expected to see way back when it was first being talked about. i got sucked in by some charts that i thought were header alone, but were not. since then, i've found that it is pretty consistent with what you can expect from any decent 4 to 1.



that being said, it would work better if it had thicker tubing, and if the collector were a bit better. however, stahl flat refused to do it. i can understand that, as the market is very small.

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[tamathumper]

But just to be clear, stock header is still required with the supercharger, yes?

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[flash]

yes. the flow gets too upset with the 4 to1. it goes all wonky. i tried everything. remember that i had a 4 to 1, and did not like the idea of removing it. i worked really hard to try to get it to work. i still don't have one on there, because i was still unable to get it to run right with it.



the stock header makes more low end torque anyway.

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[Rap]

Don't I remember you sending me a new header?

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[flash]

lol - i am finding it hard to remember what i sent to whom.



i know i sold my 4 to 1 to somebody who didn't want to supercharge.



not sure if i ever sent out an OEM header. i know i borrowed one from mark, but i think i sent it back to him.

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[Eric_Oz_S2]

[quote name='flash' timestamp='1383261315' post='151534']

yes. the flow gets too upset with the 4 to1. it goes all wonky. i tried everything. remember that i had a 4 to 1, and did not like the idea of removing it. i worked really hard to try to get it to work. i still don't have one on there, because i was still unable to get it to run right with it.



the stock header makes more low end torque anyway.

[/quote]

What's a "wonky flow"? If you ignore emissions and keep the DMe in open loop is it still a problem!

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[flash]

you can't keep the ECU in open loop. that would make everything way too rich. most of the time, even on the track, you're in a part throttle map. in open loop, you'll end up fuel washing your cylinders. these cylinders are already prone to puddling and wash. they don't need any help.



if you're willing to rebuild your motor every year or so, and it's purely a race car, you'll get a little more upper end power, but i don't recommend it, and i definitely do not recommend it for a car that is driven at all on the street. running fat is a pretty standard race car thing though. we used to do it. of course we had to rebuild our motor every season too, as the fuel was basically acting like a solvent, and the wear and tear on the rings was huge.

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[Eric_Oz_S2]

Well, I do run in open loop (i can switch too closed if I want via a dash mounted switch). I can't see fuel wash as an issue as it is not running that rich at all on PT light load settings.

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[flash]

yeah - it depends on where you are. if you've tuned it to run near stoich most of the time, then obviously you're fine. if you're running in the mid 12s on part throttle, like it would run if you just turned off the sensor, then you'll end up with a problem. it will take a while, and will depend on a lot of factors, but that will eventually cost you a rebuild. been there done that.



back to headers, one of the issues with the header i was running was the collector. it was the wrong size for the main tubes. it was as big as would fit though, so i was stuck. also, the tubing thickness was not enough. besides the horrible tone, it didn't scavenge as well as it needed to. it was probably fine at the flow of a naturally aspirated engine, but once i started really running through it, it pretty much fell down. like i said, i tried a bunch of tricks, but just couldn't get it right. in the end, i made more power with the tri-y than the 4-1, and didn't lose the bottom end like i did with the 4-1.



but feel free to ignore all of that, the number of systems i had built, the 200 or so dyno pulls, and the countless hours of tuning. who knows? you may come up with something. it happens. in a perfect world, i'd probably run a bored out S2 manifold, disable the variocam, alter the cam overlap, and solve a lot of the problems

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[Eric_Oz_S2]

I just saw that there is a new stainless steel header system out from Michael mount. See the other site for more

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[Mark]

[quote name='flash' timestamp='1383317724' post='151559']

lol - i am finding it hard to remember what i sent to whom.



i know i sold my 4 to 1 to somebody who didn't want to supercharge.



not sure if i ever sent out an OEM header.  i know i borrowed one from mark, but i think i sent it back to him.

You sent me back the part of the header you had, As to adding the Stahl header I recommend you consider a chip from Pete (if he is back in business) or getting a tune if you add it, It was not my only mod when I got it but Pete does have chip designed for use with the header and catback.[/quote]

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