Just some information I thought some of you might want to know. Got back from the dyno this weekend and have some interesting numbers. From the last time I went the temperature is now about 35-40 degrees warmer than it was. Last time was an unusually cold day in Florida. Anyway, dynoed in at 209 hp and 134 lb/ft. With the Denso Iridium plugs picked up between 2 and 4 hp across the range but idled better and V-Tec transition smoothed out a great deal. Removed air intake infront of TB and gained NOTHING. Also removed exhaust from cat back and picked up about 1.5 hp,not very significant at all. Also did first oil change to Mobil 1 and lost 2 hp with new oil.

 

Can a chasis dynometer resolve 1.5 hp? I thought the guage of reliability and reproducability was greater than that... So, anything under 5hp was due to 'margin of error'.

Please correct me!

 

To be honest, I can't really answer that question. I do know that the shop that I use just got a new version of the dyno software and it seems to be very accurate. We ran several baseline runs ahead of time and all were pretty much identical. The machine measures A/F, engine temp, air temp and many other things and we tried to make sure that all runs were done at the same conditions (engine temp., etc.) and since the 1.5 hp gain was the same on two different S2000's, I'm pretty sure that it is accurate. Makes me wonder how some are claiming larger gains from just an exhaust.

 

[QUOTE]Originally posted by shaner
[B]Can a chasis dynometer resolve 1.5 hp?

 

First off, I agree that you can't measure a 1.5 hp gain/loss on a dyno... When I last dyno'ed last year, I found as much as a 5 hp or more difference between baseline runs. As the engine heats up/cools down, it will make more or less power.

Second, a car with an open cat/header will often underperform a car with a stock exhaust system (not just an S2000 thing). I'm no physicist, so I don't fully understand all the pressure waves and thermodynamics involved, but I do know that when I used to run my integra with the exhaust system removed, the car was noticably slower than stock. A properly sized, proper length exhuast system with minimally restrictive mufflers of the proper size will generally make power over no exhaust at all. Try dyno'ing with no header - you'll lose lots of power. That doesn't mean you can't make power with a good header.

 

[QUOTE]Originally posted by The Reverend
[B]First off, I agree that you can't measure a 1.5 hp gain/loss on a dyno...

 

Its in the tuning! Just like the intake runners are tuned, so is the exaust, not necissarily back pressure but an exaust of the right dimensions will help each pulse be in the right place allowing a smoother flow.