Missmatched combo performing very well?

[cjperformance]

This is why I don't agree with using track times to prove horse power, as a nitrous racer I have seen cars get faster based on a good working combo and go slower with increased horse power. MPH may be a better indicator but that would mean that my 11.1 306 on a 300 shot made more HP than my 13.1 379 on a 300 shot, all other pieces except compression and cubic inch being the same and I have a hard time believing that.

Heads , cam, intake the same? Rpm the same?

[GARY C]

This is why I don't agree with using track times to prove horse power, as a nitrous racer I have seen cars get faster based on a good working combo and go slower with increased horse power. MPH may be a better indicator but that would mean that my 11.1 306 on a 300 shot made more HP than my 13.1 379 on a 300 shot, all other pieces except compression and cubic inch being the same and I have a hard time believing that.

Heads , cam, intake the same? Rpm the same?

Yes! the only difference was the short block... The car was about a second slower 1/8 mile straight motor, about the same on a 150 shot but quicker and faster on a 2 stage 300 shot.
Edit! I actually think the smaller engine would have been even faster if I shifted higher, it would lug a bit on shift at 7200 rpm.

[F-BIRD'88]

your 1/4 mph does not convert yo the 1/8 th mph and neither does the other lane...

Eithrr serious tail wind or down hill track or mph clocks are off.

1/8 mph x1.23 = 1/4 mph.

HThe 1/8 mph matches the poeer and weight The 1/4 mph does not.

It is way off.

[MELWAY]

Don't get too excited by heathcote mph. Both lanes came up with bullshit that weekend

I wouldn't say a total mis match. When the heads get more efficient. Less cam is needed.

I have denied some small comp wedge engines with pretty big heads and u was surprised how small the cams were for the rpm

[peejay]

I bet a lot of the "surprising results" is the long and flat HP curve! It may peak at 530hp but it is running close to that 530hp for most of each gear, most cars that make 530hp peak are well off of that, and you'd need a "normal" 600+hp engine to make the same in-gear average HP.

I'm a big fan of engines that have a long and fat HP curve/table for just this reason. They feel great after every shift, it's almost hydraulic feeling the way the car just keeps pulling and pulling.

[1mach]

Yeah, sorry about that, 530.9 - 6500rpm, the 2nd 530.4 peak is 7500rpm.

RPM_____ftlb_____BHp
3750----384.2---274.3
4000----405.2---308.6
4250----416.0---336.6
4500----419.2---359.2
4750----425.0---384.4
5000----430.0---409.4
5250----431.6---431.4
5500----426.8---447.0
5750----423.5---463.7
6000----425.3---485.9
6250----437.3---520.4
6500----429.0---530.9
6750----408.4---524.9
7000----394.6---525.9
7250----382.7---528.3
7500----371.4---530.4
7750----351.3---518.4

The torque curve takes two hits at 5250RPM ----431.6FtIb---431.4Bhp and at 6250RPM ----437.3FtLb---520.4Bhp this caught my eye the first time i glanced at the dyno spreadsheet same as the horsepower at 6500RPM ----429.0FtIb---530.9Bhp and 7500RPM ----371.4FtLb---530.4Bhp , thought about it all night ??? WHY??? is it the dyno or is it the tune ???

As far as someone mention the racetrack condition on the day , I cant find the weather details for that day at Heathcote Park Raceway weather report on 7th May 2016@12-57pm.

The track ET and MPH suggest the engine is producing more horsepower than what the engine dyno number suggest.

This is a 308 stroker'ed 355 cuin" bore 4.02 inch stroke 3.5 inch" , heads i'm guessing the VN EFI style of heads that flow 300CFM+plus with Valves are 2.055/1.625" intake/exhaust with MCSA 2.45" ........ etc. Maybe a harrop style single plane manifold????

The engine demand would suggest at 7500RPM - 7700RPM correlates with intake port size of MCSA 2.45" , would like to see all the flow figures of the heads to pass my further thoughts on the subject.

I'm assuming some of the specifications of the engine here as i don't have the full details, if you care to share more details that would be great.

Will still be thinking on why such a huge discrepancy from engine dyno to track results.

[BrazilianZ28Camaro]

What car is this engine in?

Are you sure the car isn't lighter than 3400 lbs?

[1mach]

What car is this engine in?

Are you sure the car isn't lighter than 3400 lbs?

The weight thought run through my mind as well. if the vehicle has a weighbridge docket to confirm exact weight. LH/LX no maybe a HQ series or a Commodore ? don't know this factor at all, that why I asked for more details.

[KnightEngines]

James - mph in the left lane was completely up the shit, but the right lane was reading within 1mph of AIR - another guy I went over with got a chance to run at AIR last year in the brief period it was up & running, ET & mph matched the right lane at heathcote, so if it was off it wasn't by much.

Car is a full weight VN SS with all the fruit, street car, only changes from street trim were to drop the exhaust & fit slicks.
I'm being conservative on the race weight, with driver it may be a little more - will be weighed this weekend with corner scales to know for sure.

Motor has VN heads, 2.055 & 1.625" valves, 2.45" MCSA.
Intake is a TP pro paw.
4.03" stroke, 3.48" bore.

The two power peaks had me scratching my head a little back when we dyno'd it, I figure it's a weird byproduct of the tri-Y headers, long untuned collectors that we ran on the dyno, large intake with fairly short runners & cam timing all conspiring to give 2 peaks.

Good chance the motor picked up a little with shorter collectors than we ran on the dyno, it also gained a vac pump, but that won't have bumped it up the amount we're seeing.

Could well be a combination of the long power curve keeping it pretty damn close to peak power the whole run combined with a little extra power from headers & vac pump.

[GARY C]

Good chance the motor picked up a little with shorter collectors than we ran on the dyno, it also gained a vac pump, but that won't have bumped it up the amount we're seeing.

Those two alone could be every bit of the difference...Why someone would dyno test an engine different from the way it will be run in the car makes no since to me...Why even dyno it?

Thats like building and dynoing an engine and then changing the heads before putting it in the car and then trying to compare the dyno results to the track times.

[KnightEngines]

Collector change was just what had to happen to hook it up on the dyno.

Vac pump came at a later date - motor was dyno'd a good 2-3 years ago, car took a while to get onto the road (new baby etc - always slows guys down).
Been on the road for a little while now, vac pump was added mostly to keep moisture out of the oil while street driving as it runs on E85, pulling about 8" of vac.
We haven't had a strip available on a regular basis since '05 - opportunities to race are slim pickings.
That should change within a year or so with a couple of new tracks being built within an hour of the city.

Heathcote is an 8 hour drive, longer if you're towing a car!

[1mach]

I would of changed gears at 6300RPM based on the engine dyno result " 6500RPM ----429.0FtIb---530.9Bhp " maybe run faster again. BUT
the header change stuffs things up.

As Gary said, what one is planning on running on the vehicle should be run on the engine dyno.
Definitely exhaust can kill the power as we all are aware. be nice to run back to back headers on a
chassis dyno but a lot of work just to prove one point of the puzzle

What was the E85 A/F ratio set on the dyno for wide open throttle ?
Does the car run a bonnet scoop of some sort ?
Did they run a A/F ratio meter at the track ?
What results did you get when you plugged all the details in PipeMax for engine combination.

[GARY C]

Collector change was just what had to happen to hook it up on the dyno.

Vac pump came at a later date - motor was dyno'd a good 2-3 years ago, car took a while to get onto the road (new baby etc - always slows guys down).
Been on the road for a little while now, vac pump was added mostly to keep moisture out of the oil while street driving as it runs on E85, pulling about 8" of vac.
We haven't had a strip available on a regular basis since '05 - opportunities to race are slim pickings.
That should change within a year or so with a couple of new tracks being built within an hour of the city.

Heathcote is an 8 hour drive, longer if you're towing a car!

I understand, I am sorry to be such an A$$ but I am!

I have been following this thread and then in one sentence you hit me with a 30 to 120 horse possible change in the combo and I loose my F-en mind... But I am doing much better now.

[GARY C]

As Gary said, what one is planning on running on the vehicle should be run on the engine dyno.
Definitely exhaust can kill the power as we all are aware. be nice to run back to back headers on a
chassis dyno but a lot of work just to prove one point of the puzzle

Yes, sorry to freak out but I have seen several reputable sources prove 60 ft lbs on collector length alone. Larry/PipeMax for one!
I personally witnessed a test on a BBC with an electric vac pump when people were trying to figure out how to make them survive that was good for almost 50 hp.

On one combo I know of the best they could do with the header allowed by rules for the chassis was down over 20 horse vs what could be done with a dyno header.

[KnightEngines]

Collectors didn't change that much - typically I'd expect to see 8-12hp from the change on an engine like this.
Vac pump is maybe good for 10hp - motor does not run a low tension ring pack or gas porting or anything like that to take advantage of the vac pump, it was not built with a vac pump in mind.
So the motor is maybe/probably up 20hp or so from the dyno with the changes, not enough to explain the on track difference.