[65Z01]

I just posted in the "Engine" section of "Reviews" a link to some L98 mods test results data.

Though the data isn't product specific and covers a series of mods, I thought that would be the best spot for that sort of info. On the "other forum" I've seen a lot of posts wanting info on L98 mods and thought this data would be useful to those getting into the performance aspect of their C4.

My thinking was that in that section the data would be available for a long while; if I was in error on the placement, moderators please adivse.

 

[Patrick]

I just posted in the "Engine" section of "Reviews" a link to some L98 mods test results data.

Though the data isn't product specific and covers a series of mods, I thought that would be the best spot for that sort of info. On the "other forum" I've seen a lot of posts wanting info on L98 mods and thought this data would be useful to those getting into the performance aspect of their C4.

My thinking was that in that section the data would be available for a long while; if I was in error on the placement, moderators please adivse.

I saw that, cool info. I'll have our "Corvette links" page up shortly, and that'll allow us to post the links to great Corvette websites!

 

[Onyx Black]

Great link! I love it when someone documents their mods, it is very informative for this rest of us.

 

[War Machine]

I'm very skeptical of that Test Data page. If I go by that, I should be running mid 12's the next time I go out to the track. I seriously doubt that is gonna happen.

He gained over 3 tenths from Air Foil, Bosch Plugs, TPIS wires, K&N cut lid, Stage II EPROM, 170deg Stat. and gained over .25 w/ a cat-back??

I did all that and more and only saw a .15 gain on ET and 1 mph. See why I'm sceptical of that?

In my homepage, I don't have airfoil listed but it was used for the first 2 Operations. I don't have it in right now but I will bust that sucker out come dyno day and see if there really is a gain. I didn't think of taking it out when I dynoed last time.

 

[BubbleHead]

You have to keep in mind the variances between each car. I know of a stock C5 that ran as fast as a C5 with a heads and cam package.

I haven't looked at the link yet but you also have to consider track conditions, weather, operating temps, etc...

It sounds like this website maybe a nice "guide", not the L98 performance bible.

 

[65Z01]

Indeed those numbers are more of a guide as to what to expect from $$ invested, relatively. In some cases I did not see the gains mentioned; in others more gains. Though I have the #113 heads on my '88 L98 I don't have the flat-top pistons that their '90 L98 had so HP is down a little. I believe gains can vary somewhat depending on the particlular of the L98 being modded.

For example, I race with Vic'89 on the "other forum" and he gained the listed numbers when he did the LT runners & BM base mod, and maybe a wee bit more.

Also you need to be able to launch in your power band as it changes with mods and raise your shift points as top end power improves. They were using a stick shift launched at 3,000rpm...well into the power band.

Don't foreget too that the results of mods tend to depend on when done in a series of upgrades.

I run on a sea level track (Raceway Park at Englishtown, NJ) and the numbers in my sig represent best passes with "excellent" weather. I have some equations on my site to normalize trap speed (and so chp estimates) for weather conditions. I don't think that data was so normalized however.

However even with these variables, I believe that if I do the heads, cam and headers mods I will see gains comperable to those listed, i.e a total gain of about 60-70chp, which should be enough to run consistently in the mid 12s.

Of course there are a copla free mods not mentioned in the article, like cut-back spark plug electrodes (10hp) and toss the "frisbee" (from '88-'91 L98s) (10hp), drop from 170deg to 160def stat for another few hp gain (30deg F ~10chp).

Anyway, I hope it will be interesting and useful info for fellow L98 owners.

War Machine, what is your launch RPM; are you running DRs? The only short time I saw on your site was 2.10sec and assume that has dropped by now. I should think that those mods will get you very close to 12s; apply the weather corrections and see what happens to the numbers.

 

[War Machine]

I haven't been on a track since Aug. or Sept. 2001. I think my best 60ft on the Firehawk's was 2.07 or something like that and I launched from idle. I'm shooting for 1.9's by the end of the season as I wear more rubber of the tires.

I've never done any wx or altitude corrections to my times but I will now just to see what it is. I know that Rt.66 is 650ft above sea level so that should amount to something.

My car was down last year the week before Rt.66 opened and didn't get it running til December. Running but not track ready. It'll finally be ready by the end of next month. That being said I will have to re-learn launching with my new mods. Hopefully I can make the decision whether to manual shift launch or auto launch by the next time I T&T. Right now manual launch feels good(minimal wheel spin on street tires) but the trans is going to be worked on soon.

 

[65Z01]

That elevation is a negative factor as is low baro, high humidity & high temps. The only to realy compare track data is with normalization for weather. Of course I save those time slips from runs in "great weather".

I've also found that ET & trap speed are lower if coolant temp is over 160deg, as it can get while idling in the lanes on a hot day.

I was told by a guy at the strip that launching with the chassis preloaded (high idle) is beneifcial; and by my tranny guy that is fine but to just stay a few hundred RPM below TC stall to aviod turbulence in the fluid and so maximize torque multiplication.

I picked up a 10th of so by raising my launch RPM from idle to 1,700-1,800 RPM.

Good luck with the latest mods.

 

[War Machine]

Jim,

Thanks for the tip! :cheers:

I can't wait til I get back on the strip! :excited: