Time to go Stage II!
- Thread starter Alky V6
- Start date
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2500 rpm stall? Where did you get that figure from?Sorry I did not realize your 2500 stall is top secret...............I think that what you mentioned you used on the stage 1. Please give more details on the slip % if you can.
The 9.5 that I've been using lately with the Stage I stalled anywhere from 3,200 to 6,200 rpm. 3,200 stall would be on the engine only, with no help from nitrous, afterburn, or boost.
I'm not sure what you're asking for with the slip %.
You told me years back its 2500-2600, and you refused to put more stall in as I recall, but that is old news. Its very easy to figure slip % mph vs rpm at the traps, from the theoretical calculated rpm, from your old data logs, where did you come up with the 12%?
The last time I used that low of a stall was with the 10" Neal Chance and the smaller T76 turbocharger. A combination that worked very well. That was years ago. You must be going through some old threads.
The 12% slip figure was worked out from datalogs and working with the drag sim to get the sim to match datalogs and timeslips.
Where did you think I got the 12% figure from? The sim alone? When I had all those datalogs and timeslips at my disposal?
Ok, I get your point. However, I thought 4-5% was the average for the 9.5" converters. Are you not throwing away 7% HP by having the converter so loose?
Could be. Dusty would be the one to give us a better idea of how much E.T. and mph there is to be had with less TC slippage in a case like mine. Although, I'm sure he'd want to have some real world data on this new engine combination before he put on his thinking cap on this one.
With the changes in power with this new engine setup, we'll see what this 9.5" that I have now can do. If you remember from my past discussions on torque converters, I like to keep the dialing in of the torque converter for last. Working up the car and getting to that point where you're ready to fine tune the torque converter is like eating through the main course knowing that you have this delicious desert still to eat at the end.
Dusty Bradford
Well-Known Member
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- May 24, 2001
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It's possible to have 1-2% slip but it never necessarily means the car will go faster. On a race application often times 6-9% is optimal for the best et. Lower slip may put more power to the tires but the engine will most likely be pulled down out of it's rpm range. The only converters I have spec'd with the intention of 1% slip is for the dyno competitions. Those cars are a slug at the drag strip unless they change converters. For a car like Dons with his 9000 rpm range, lighter weight and lower rear gear, it would be one of the loosest 9.5's I would build. Too loose for the average TSO combo but the requirements are totally different.
I received a responce on the question about the engine simulator. The pressure and velocity traces in the output are NOT representing a multi-cylinder model.
His complete responce follows.
Mon Aug 20, 2012 8:39am
"VERY sorry about late reply. In the Engine Analyzer Pro, we are analyzing just one cylinder's pressure and velocity in the runners. What you are requesting would be what a true, multi-cylinder model would do, which we are not doing.
However, behind the scenes, we do some additional "tuning" based on the intake manifold secondary tuning characteristics. This includes plenum volume, secondary runner length and size, etc. We also do some of this on the exhaust also, but both on the intake and exhaust this "tuning" is quite simplistic." -Kevin Gertgen
His complete responce follows.
Mon Aug 20, 2012 8:39am
"VERY sorry about late reply. In the Engine Analyzer Pro, we are analyzing just one cylinder's pressure and velocity in the runners. What you are requesting would be what a true, multi-cylinder model would do, which we are not doing.
However, behind the scenes, we do some additional "tuning" based on the intake manifold secondary tuning characteristics. This includes plenum volume, secondary runner length and size, etc. We also do some of this on the exhaust also, but both on the intake and exhaust this "tuning" is quite simplistic." -Kevin Gertgen
This could very well be why, in my particular case with the Stage I build, I had to tweak the head flow numbers so much to get the simulator to match real world performance results. The simulator simply was not taking into account some sort of manifold tuning advantage that I had stumbled across.
I would love to see what a multi-cylinder simulator model might show.
I would love to see what a multi-cylinder simulator model might show.
I hope before Obama feels the boot of the American people on his rearend.
I don;t think he will be elected back in , and I am a Canadian even
Dusty and I have been conversing, and it made me revisit the engine power curve I was using in the drag sim. I think I've come up with something more realistic for the new engine.
Using the new power curve in the drag sim, it is showing that going with a tighter TC would slow the car down. And, going with a looser TC would lower the E.T and the MPH. Just a little, though, so the TC I'm using now might be real close to what's needed with the new engine.
New performance prediction.
Assuming a peak of 1,530 bhp.
7.875 @ 172.24 in the 1/4.
5.014 @ 137.03 in the 1/8.
1.144 60 foot.
Launch rpm and bhp: 5,190 rpm and 545 bhp
Shift points: 9,000 rpm
RPM across the finish line: 7,938 at the 1/8, 8,677 rpm at the 1/4.
TC slip;
Top of 1st: 10%
Top of 2nd: 9%
1/8 mile marker: 20%
1/4 mile marker: 12%
Trying different slip factors with the sim, the optimum slip for my combination to obtain the best E.T. looks to be 13%. A 6.5 slip factor in the sim, rather than the currently used 5.8. The difference between the two slip factors is 0.012 sec. E.T. and 0.19 mph.
Using the new power curve in the drag sim, it is showing that going with a tighter TC would slow the car down. And, going with a looser TC would lower the E.T and the MPH. Just a little, though, so the TC I'm using now might be real close to what's needed with the new engine.
New performance prediction.
Assuming a peak of 1,530 bhp.
7.875 @ 172.24 in the 1/4.
5.014 @ 137.03 in the 1/8.
1.144 60 foot.
Launch rpm and bhp: 5,190 rpm and 545 bhp
Shift points: 9,000 rpm
RPM across the finish line: 7,938 at the 1/8, 8,677 rpm at the 1/4.
TC slip;
Top of 1st: 10%
Top of 2nd: 9%
1/8 mile marker: 20%
1/4 mile marker: 12%
Trying different slip factors with the sim, the optimum slip for my combination to obtain the best E.T. looks to be 13%. A 6.5 slip factor in the sim, rather than the currently used 5.8. The difference between the two slip factors is 0.012 sec. E.T. and 0.19 mph.
The sim is showing that a switch from the present 3.73 gearset to a 4.10 gearset would make the car quicker by less than a tenth. TC slip would be 10% crossing the 1/4 at 9,378 rpm. Not worth going after for the extra wear and tear.
I tried the 4.10 gearset with the looser TC (6.5 factor) and the difference in performance was miniscule. So, if I really wanted to go after those last hundreths of a second, I would either go with the slightly looser TC or the lower rearend gearset, but not both.
I tried the 4.10 gearset with the looser TC (6.5 factor) and the difference in performance was miniscule. So, if I really wanted to go after those last hundreths of a second, I would either go with the slightly looser TC or the lower rearend gearset, but not both.
Getting that good of a 60 foot is going to depend on how quickly the engine rpm and power can be ramped in once off the line. The predicted 1.14 is a best case scenario where the engine is able to come in with the right ramp up of power, and the tires I'm using now hold onto the track. This prediction did account for a little bit of tire slippage at the launch. I did not use the 'perfect track condition' option in the sim for this 1.14 prediction.
With the new engine, torque will be on a rise once the car leaves the line. Whereas with the last engine, torque was on the decline after the car left the line. It's just the difference in the power curves between the two engine configurations.
The new engine should be able to keep the chassis loaded better and the tires planted. Hopefully, anyway.
This new engine setup will be a good test to see how quickly it can get this 91mm spooled up once the car leaves the line. More cubes would have helped this situation, but I've already discussed why I didn't want to go with a stroked crank.
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