How much HP gain by removing cats?

[QB93Z]

I attended an event called Vintage Thunder - A Day at the Races put on by the Mason Dixon Chapter of NCRS. It was held at Cecil County Dragway in North Eastern Maryland. We spent the morning making time trial 1/4 mile runs and then had a single-elimination bracket race in the afternoon.

I had the only ZR-1 there. The crowd was mostly C5 and C6, but there were a few olders Corvettes as well.

The event was very well run. Thanks to the Mason Dixon Chapter of NCRS for putting it on.

This was my second outing at the drag strip running my 1993 ZR-1. This time was different because I removed my catalytic converters. The change in performance was dramatic compared to last month in Beech Bend. (Not my performance, the car's. My 60 foot times still suck.)

My best run run was a 12.9 at 112.8 mph. My best top speed was 115.7 mph.

The average ET improved .13 seconds and the average top speed went up by 4.1 mph (109.78 to 113.87).

I have a stock LT5 with headers, 4.10 rear end and a Corsa exhaust.

Removing the cats did not improve my 60 foot times at all. No surprise there!

In the past I have seen a comparision of the HP needed to change quarter-mile top speed. Can anyone estimate the HP gain I got by removing the cats?

Thanks,
Jim

[Pete]

Jim 4MPH is about 50-60hp my opinion i don't think just CATS alone will give you 50-60HP unless you had bad CATS.

You have to make sure you didn't change your driving habits,i.e. shift points (rpm),power shift,tire slip at shift points,etc.
Also what is the elavation at Maryland over BG? i think BG is 600 or 700ft above sea level.

The other thing that comes to mind compare the timeslips from one run to another if you have a better 60ft you will get better MPH.

Pete

[flyin ryan]

what's the altitude there?

[QB93Z]

The altitude at Cecil County Dragway is propably less than 75 feet, but I don't know for sure. The temperature was about 10 degrees hotter at Cecil County. (The temp printed on the time slips was 167 degrees, which is what it felt like in the car after 14 passes.)

I agree about the 60' times being a factor, but my average 60' time in Beech Bend was 2.275 and average 60' time in Cecil County was 2.277, essentially the same.

I might have improved my shifting but probably not much. I didn't try to change my technique.

Maybe Cecil County Dragway runs down hill.

I didn't change anything else on the car or engine since Beech Bend. I did wash it real well after driving home from Kentucky in the rain.

I recorded two of my runs on my laptop and at Cecil County the Knock Count was zero during the runs, so I was not getting and spark retard from that. At Beech Bend I didn't record the runs, but recorded the dyno runs that morning and got zero knock count also.
Jim

[GrayZ]

Jim:

I asked Marc Haibeck the same question, when he was
refitting my corsa exhaust system.. I have Random tech
hi flow cats, he explained, 2 to 4 horsepower difference, W/o
but as Jeffvette expunged in a parking lot discussion,
not worth the smell.

[flyin ryan]

Originally Posted by QB93Z

after 14 passes

I agree about the 60' times being a factor, but my average 60' time in Beech Bend was 2.275 and average 60' time in Cecil County was 2.277, essentially the same.


Jim

you got 14 passes in ONE day? WOW. we'd be lucky to get half that in a day. the times i posted for Craigs427 yesterday, he is right around the 2oh's 60'. 2.08-2.09 i think. i know Hammer has good 60's. hard to compare his car though, it's on another planet considering it's minimal changes.

[QB93Z]

Originally Posted by flyin ryan

you got 14 passes in ONE day? WOW. we'd be lucky to get half that in a day. the times i posted for Craigs427 yesterday, he is right around the 2oh's 60'. 2.08-2.09 i think. i know Hammer has good 60's. hard to compare his car though, it's on another planet considering it's minimal changes.

I saw your other thread. Those are good times. I need to work on launching better. But, you know what, it is a hell of a lot of fun at any speed!

Jim