robz

If I don't sell my car I'll likely do heads and although I don't care much for dyno numbers I'll be sure to post them.

jleews6

I would have to think that 550 to 570 whp would have to be in the high 130s in your car. That would be cool to see.

NemesisC5

Rob, curious as to why I read of more 8k de-stroked LS7's than 8k LS1/2/3's with the same stroke but smaller bore? It seems the smaller bore motors would be on equal terms as far as ability to rev. Also more abundant numbers of smaller bore motors with owners chasing lower et's/higher dyno numbers actually needing more rpm's to hit lower et's/higher dyno numbers (as being discussed in this thread). Only reasoning that comes to mind is the LS7 rectangular port heads and intake ability to flow more/breathe higher in rpms....BUT the larger bore needs more air so it seems that angle would be nullified.

robz

Not really sure.
I like the big bore to allow for more power especially since the small stroke takes away ci but allows for high rpm. Obviously there's alot more to it.

robz

570+ with a radial is more like high 140's.

NemesisC5

This post in C6 Tech is remarkably similar to the discussion here.


Heads And Cam Stock Block LS3 Dyno Results....

robz

Good catch.
And there's a bit more in that setup as well.

NemesisC5

I thought you'd like that.
It seems they are not quite as ready to take the rpms up high yet but I think in time more will embrace it especially on new builds.
Spin to Win!

robz

Some of us spin the hydraulic stuff well over 7000 rpms with reliability.
Going to a solid roller cam and supporting mods would prompt me to design the setup to spin the motor to 7500 rpms and more.
Plus if you make max power at 7000 rpms you should be shifting it higher for best et.

robz

Heres some info I posted in another thread that may benefit some of you drag racers by helping establish shift points. There are huge gains to be had if you get this right. Do your PUC calculations and that will get you in the ballpark, then fine tune at the track. A g-meter is one of the best tools to confirm that your putting the power to the ground. If you are confident you have the max power under the curve at the rpm band you will be racing in and don't see much gains in et and mph then you need to optimize your setup for the drag strip and a g-meter can tell you this. The most common cause of this is excessive wheelspin.


Just to drive the point home about power under the curve here's another example for anyone who wants additional info.





This particular dyno pull stops at 7300rpms.
Use all your resources to predict what the car does beyond the dyno max rpm if you don't want to pull any higher.
Assuming this is a well designed and sorted out setup I drew in pencil the estimated power curve beyond 7300rpms up to 8000+ as one possible scenario. (Of course you need have some reliable data and experience to do such an estimation. Some setups drop off hard after 7000rpms due to instability. This one doesn't.)
Now find out how much your car drops in rpm in each gear on the drag strip.

To keep it simple and "on the lines" let's use 1900rpms.

Without even doing the math you can easily see that if you shifted @ 6920rpms (which some people feel is high) you would be giving up a huge amount of power throughout the entire gear.
6920rpms would fall back to 5020rpms and the hp at that recovery rpm is low.

Now pick 8060rpms as a potential shift point. The rpm falls back to 6160rpms. Look how much power under the curve is in this range. We are talking about a difference of an average of ~ 40whp throughout the entire pass. I would say you could be losing several tenths in et if you are shifting @ 6800 vs 8000 rpms in this case. And for those who are infatuated with torque you can also see how the shift recovery rpm is droping back still very close to peak torque, so perhaps an added bonus.
This is the game you must play if you want to run low et's and high mph. This car should be shifted above 8000rpms for maximum potential hp. And if you want to get even more detailed you can do the calculation for each gear and shift according in each individual gear with a variable shift light. Making the power is only part of the equation. Knowing how to apply it to the drag strip is equally as important. Then finally being able to put it to the ground is the final piece of the puzzle.

And of course the entire setup needs to be designed to handle the rpm you plan to race at without exception.
It's also of paramount importance that anything you estimate must be based on a large population of accurate data for all this to work.
Hope this helps.

493lszosix

This is interesting stuff Rob because I've been trying to figure out where to shift and have been clueless, my question is when I shift am I trying to land at my peak torque or is that not a factor, or am I trying to shift so that I land back in as high of a HP range that I can

I've been reading your write ups on launching and slipping the clutch which I think is going to help me some this upcoming race season too but that's another topic

robz

It's all about power under the curve as I mentioned above.
Landing back on peak torque is not the goal but it can be a small bonus.
It's good to have your launch bog down to peak torque if possible but there are a lot of other things to consider too.

With many LS setups shifting higher is often the answer but prove it to yourself by doing the math.

Power under the curve

Your rpm drop will be around 2200rpms. You can check on a log and calculate this for each gear. Get your dyno data every 100 rpms and average it out in several 2200rpm zones. It helps a great deal if you can see what happens several hundred rpm after peak hp if you and your tuner are comfortable with that and at least one pull. Whatever has the highest average power under the curve is the area you should be running in for the most part.

Consider track conditions and other mods that show up on the track and not the dyno as possible modifiers and adjust from there. You should use a shift light and accurate data always to draw proper conclusions. Mph and et can help you dial things in as long as you are comparing apples to apples. A gmeter is a cool tool that eliminates many variables and can hone in your shift points on the track.

lambert55

I don't know if this is the right thread but here goes. C5 Z track car engine swap and tuning. The stock Ls6 blew up and I bought a replacement motor and installed it. Ready to fire it up. The new motor has a medium cam, Fast 92, ram air intake, long tube LGs, CNC ported 243 heads intake matchup. Stock valve sizes. Equipped with wide band oxygen sensor diplay. I know so little about tuning that I am seeking advice about waht to do? Should I crank and run it a bit then take it to a tuner/dyno? Or should I crank at the dyno shop? Any recommendations on tuners? The car will be raced in NASA so street drive ability is not a concern. Thanks for giving a newbie advice.

Scotty2000SS

I look at the C5Z bolt on fast list all the time. I see most C5 bolt on cars running mid 11's. Now I'm sure they don't have all the bolt ons to get to bottom 11's but how reliable is the stock pushrods for spinning the engine higher? Only reason I ask is beacuse I'll be shooting for a spot on the top of that list one day and I'll take all the advice I can get.

NemesisC5

Bolt on would exclude cam or heads and the stock pushrods should handle stock valvetrain at any rpm below valve float.

robz

Did you get the car fired up and tuned?
When does the race series start?

nskyline34

So who is going to throw down the first build and hp #'s? Its all just smoke and mirrors unless people start ponying up pennies and hitting the rollers.

I cant manage to break 500 even though I basically did what the OP wanted to - Max effort on a stock bottom end... 487 isnt even in the ball park...and as of yet the ****er doesnt even idle well enough to drive...

Scotty2000SS

I see this all too often. Although every dyno is different the trap speed is the tell all IMO. I had a cam only LS1 Z28 convertible that made just over 400 RWHP and trapped 116.xx with a terrible set up. I was still on stock heads (241) and had an LS7 clutch. Over the years I've learned why it didn't trap higher. Race weight for starters, heavy TT2 wheels, clutch, ect..


What's the set up?

lambert55

It started up right away and sounds great. It won't idle but it is a really quick revving engine. I got delayed on taking it to the dyno by paint and body work. I am going to post my dyno sheet on this thread. David

robz

The original point of starting this thread was to emphasize that dyno numbers are just numbers and that you can find ways to make huge peak dyno numbers if you focus on that but it's not the way to build an fast, efficient, reliable setup.
Build a car for what you like to do and support it with parts that will make it most efficient in the rpm band you will be racing it in. The test it on the track of your choice and make adjustments based on the real world data you obtain.

I fully understand that dyno numbers are popular and that will never go away. It's fun to compare them and throw parts at a particular setup to see how much more it makes. It just more fun to take it a step further to a track and try and figure out what it takes to make it a top performer.