dan_uk

well max a few months between dyno sessions.. the dyno is SAE corrected

To be honest if there is any error I think its the other way making the 70mm read lower because it feels a lot quicker and my laptimes at the local track picked up to

How do you explain the AFR's? I mean it was - 10-15% correction up top with the VAFC with the testpipe + stock exhaust and about -2% with the 70mm

Without the VAFC you are talking at least a 7HP difference between stock + testpipe and 70mm + 70mm testpipe on my car

Gernby

I don't think the T1R header is crap, since I've made good gains with it. However, it does seem to be more oriented toward low end torque. It smooths out the torque curve more than the stock header. The stock header is tuned for a surge in torque at 5500 RPMs, even if VTEC is engaged at 3500. There's still gains with VTEC at 3500, but you can still feel the "hump" at 5500. That doesn't happen with the T1R.

I would LOVE to get my hands on an HFC to test, but am not willing to buy one just for a test. I tried finding someone local that would loan me one, but noone offered.

Gernby

I would think that 12 months would have been better than a few months, at least where I live. A few months difference means a big change in climate, and maybe even a change in fuel content. SAE corrections aren't perfect, and don't do ANYTHING for fluid temps or heat soak.

I couldn't explain your AFR's, since you didn't provide any numbers. However, VAFC's are shit. I had one on my '02 (with a wideband O2), and it never stayed in tune. You could tune it on a dyno, and get nice gains with a smooth, flat AFR, then go back to the same dyno a few weeks later, it the AFRs were all over the place.

I also noticed that a -10% correction on the VAFC did NOT cause a -10% change in fuel.

Gernby

I just removed the T1R header to swap the stocker back on. My caliper won't reach far enough inside the collector to measure the inside diameter of the flange, but the outside diameter is 60mm at the flange. The outer diameter of my test pipe is 61mm. The tubing used for both is very thin, so I don't think there is a decrease in diameter at all.

I'll have the OEM header back on shortly, but the snow that we have on the ground will prevent any testing. We are supposed to have an ice storm tonight, so I probably won't be able to test it tomorrow either. North Texas shuts down when we have ice on the roads.

dan_uk

Well I had the VAFC tuned/tweaked about 3 times with the stock exhaust on this dyno without and without cat and it was always leaned out at least 10% up top more like 15% most times.

Once the 70mm was on it was lean on that tune and then corrected back to around -2% basically doing nothing so I just took it out.

The stock exhaust dynos were at the start of the year then in april then the 70mm was in July which is probably the worse hottest month here.
If there is any dyno error i would say the 70mm is on the low side.

I dunno why you have a different numbers I don't doubt what you found but there must be something else going on. Maybe your stock exhaust with those mufflers just flows better and the 70mm you used is no good or was restricted by a 60mm testpipe?

H22toF20

Sorry but just bolting on the HKS 75mm is proven to make power EVERYWHERE in the powerband over the factory exhaust with the OEM computer. So it was no placebo effect.

I half agree on you with the test-pipe. I believe this to be the biggest restriction in the OEM exhaust. I'm sure I would have felt a slight difference if I bolted something like a 60mm with my 75mm, but probably no where as much as my UR 3". Why? The 60mm would still be holding back the potential flow the HKS 75mm was made for.

The exhaust can only flow as much as it's smallest diameter or biggest restriction(muffler, cat ect). A .4 inches difference(60 to 70mm) is actually a big increase for exhaust size. Until you put on a 70mm test-pipe with the 70mm exhaust, this is an unfair comparison.

bpaspi

Sure, maybe your LTFT's are correcting also in open loop
(Sorry, couldn't resist...)

Gernby

Now that's funny.

Gernby

Do you have a link to the proof about the HKS gains?

I put the stock header back on, and reloaded the same calibration that I was running last week before installing the T1R again. I went for a drive in the snow, and found that my "testing ground" was clear enough that I could safely do some runs. However, the road was very wet with some standing water, and a pretty good wind, so I would NOT consider this test to be anywhere close to the standard of yesterdays tests. Also, since it's been 8 days since the "baseline" with my modified stock exhaust, that's another reason to give some doubt.

Anyway, here is the 70mm with stock header (red) vs. the modified stock exhaust with stock header (green).


Here is the AFR curve for the same.

Gernby

BTW, VTEC engagement was at 3500 for the stock header.