Stephen,

It's been a while (I think?) since we've heard how the exhaust testing was coming along? Any new news?

Thanks.

 

Stephen cmon the suspense is killing us. How many exhausts have you tested so far?

 

i know the answer!!!!!

 

So, what's the answer?

 

Andrew...

by the big grin from your last post....let me guess....fabspeed?

 

I will be real informative if the afr's are posted with each exhaust test.

 

I should have it done next week. I have tested enough to run up a bill of about 700.00 at the dyno. I am one man short and the weather has been up and down. The last one will be this week.

 

I am on the fence about the sports exhaust I want. Either Europipe or fabspeed.

Any recommendations to help me with my choice.

RJ

 

Me 2 - although Techart 70mm is also on my choice list....

 

Stephen,

When the tests were accomplished I know each test included changing the exhaust. My question is, the car makes most of it's power with an afr of 12.9-1 to 13.3-1. If the exhaust change richen or lean the afr's above or below these numbers were the afr's then re adjusted so all tests are within the same afr's? I know from experience the difference between 11.1 and 13.1 can be about fifty HP. Changing parts usually changes the afr's.

 

Chad,
While 13.1 may be good for you it is a little on the line for the average car, not to mention you are on 100 pump. We are not. That in mind the test were all run with a target of 12.5 AFR. None were higher. The range that all the mufflers rolled in at were 12.2-12.5. Adjustments on the ECU were NOT necessary based on this small scale. Not to mention I have proven that the ECU will adjust as much as 40HP and 30 TQ on its own. The targeted AFR is what the average car will run. No doubt that the mufflers would have made more should we run a 12.9, but the truth is this is too close to the line and we are talking about cars that will simply benefit from bolting on the muffler. The idea was to keep this on a level playing field that the average user could gain something from. A 12.2-12.5 on all the mufflers is acceptable.

 

Stephen,

I agree with your assessment that 12.9 to 13.3 is producing more power. I don't agree that it is on the edge. The edge would be closer to 14.0. But it does really make a real difference if they are all in the same afr area.

As long as the afr is given along with the maximum HP at the recorded rpm. You would have to agree that brand X producing 400 rwhp with a 12.2-1 afr has the potential to produce more hp than brand Y producing 406 hp at 12.5-1 afr. The afr immediately proceeding the manimum attained would also effect the outcome. With all this information a good evaluation can be made. The fact you have established a base afr will tell alot about the exhaust. The richer the exhaust becomes because of the change, the more power the exhaust has to offer when it is tuned. Now if the car is tuned for a certain exhaust, then that exhaust would have the benefit of the afr adjustment already, correct? Please do not get me wrong. I know you have put a lot of time, money and effort into this and it is very much appreciated. I am not looking for information you don't have, but if you do have it, then it would be most appreciated. Thanks.

 

Chad,
13.1 is pushing it on the street. Experience I have on my side with this one. 13.1 also doesn't necessarily provide the biggest HP or TQ curve on all setups. We just watched a car that constantly ran 13.0-13.1 die after one track session. That is another subject for another day. No I didn't build it

I am also sorry I have to disagree with the idea that pushing each muffler to a 13.1 would have created more or less HP. We can play the what if game all day long and the truth is projects like yours are in the top .00001%. I will never tune a car for 13.1 on the street for the masses as the power and TQ has been sufficient. The bases of this exhaust were what works as a common link. The factory runs 12.-2 to 12.5 and that is what we ran. As discussed with you the car has the ability to maximize the range it is given and therefore kept things in this range. Not one muffler moved out of it. It is a possibility that the open pipes would have created more HP at 13.1.it is also possible that it may have done worse. Bottom line was the exhaust comparison was to stock, not one another and done very controlled with a common goal in mind.

 

Stephen,

I can only relate to my experiences. An afr of 12.9 to 13.1 made more hp. This was generally between 6700 and 7300 depending on the size of the intake passage and the throtle body. More torque was made with a richer mixture 12.3 to 12.5 between 4300 and 4800 rpm's, again depending on the intake and TB sizing. I run my car on 91 octane up to 1.1 bar. Above that I use 100 octane. No problems, no detonation. As A. Graham Bell's book Performance Tuning Induction Motors states, "there are two schools of thought regarding afr and maxium power." One happens to be the one you subscribe to the other happens to be the one I subscribe to. Both have their own merits along with pros and cons.

Again, the dyno runs should show exactly what the afr was at maximum torque and hp and at the corresponding rpm. It shouldn't be a range. If you have this information, it would be appreciated.

 

Well, This is one subject I will agree we disagree. No offense meant here but I have tuned and built custom injection on hundreds of cars and my experience is a tad different. Lord knows how many pulls I have done, but enough to calculate a good amount of data on AFRs. My cars don't run on 100, yet they could. We also do not set our rev limiters higher than stock so a 7300 pull would have been out of the question.

I do have the AFR numbers. You will have to wait until the article comes out. After all it WAS you that said there were 5000 ways to do this. Stick with one and don't deviate.