The Interceptor-X for N/A Cars
01-12-2006, 10:29 AM
#626
One thing I have noticed-- and my interpretation skills may be untuned---but this car has a high rolling resistance(stock tires). In neutral rolling down the hill in front of my home the car doesnt gain the speed one would think. Comparing the 8 to my sons Ford ranger p/u and, to my daughters volvo(i know front wheel drive but this is just rolling resistance--no power) it gains much less speed than theirs. I know I have wider tires but I dont think that accounts for it all. Tight can be good(lol) but sometimes it can rob power. Food for thought?
Olddragger
Olddragger
01-12-2006, 10:52 AM
#627
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DMP mentioned earlier about how it's only 4 whp averaged across the whole RPM range, which might very well be true. But if you're running hard, you're going to spend most of your time in the 6k - 9k range anyhow. Downshifting at redline in...well, pretty much any gear...isn't going to drop you more than what, 1.5k? Which is still well within the big fat white zone of improvement. Yeah, it would be cool to make that kind of increase from idle to 5k, but at least the increase is wide enough that you'll stay in it from one gear to the next (unless you skip gears or something).
01-12-2006, 11:04 AM
#628
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Originally Posted by rotarygod
I'm going to just quote SDS on this topic:
Flywheel vs. Wheel HP
As most people know, there are power losses through the drivetrain so wheel hp is always lower than flywheel hp. Front wheel drive cars with transverse engines tend to be more efficient than most rear drive configurations due to the layout of components. However most publications overestimate these losses considerably.
Most rear drive cars have a 1 to 1, 4th or 5th gear which means that the power path goes directly through the mainshaft of the transmission. The only losses here are bearing drag which is less than 0.5% and the viscous drag of the gears running through the oil which is about 1% with hot oil. Indeed, published data indicates a transmission efficiency of 98 to 98.5% for conventional transmissions in 4th gear.
Losses within the driveshaft account for about 0.5% if they are properly aligned, balanced and with fresh U-joints.
Differential losses in the commonly used Hypoid type gearset is in the order of 6 to 10%.
The worst scenario case for a rear drive setup is on the order of 12.5% in 4th gear, not the 20 -25% often published. If 25% was being lost in the drivetrain, the oil would boil in the differential housing in short order and aluminum transmission cases would fatigue and break from the temperatures generated. On a 200 hp engine, something on the order of 37,000 watts would have to be dissipated out of the transmission and differential housings. Obviously, this is not the case.
Transverse, front drive transaxles usually have no direct lockup gears and no 1 to 1 ratio, however, since the torque path is never turned 90 degrees as in the rear drive setup and efficient helical gears are usually employed for the final drive set, losses are more on the order of 6 to 9 percent in the upper ratios.
Tire pressure and wheel alignment can have very significant effects on losses at the rollers. Tire pressures should be set the same between each test. Tire rolling resistance varies inversely with speed, another factor not taken into account by most chassis dynos when applying phantom flywheel hp formulas.
Flywheel vs. Wheel HP
As most people know, there are power losses through the drivetrain so wheel hp is always lower than flywheel hp. Front wheel drive cars with transverse engines tend to be more efficient than most rear drive configurations due to the layout of components. However most publications overestimate these losses considerably.
Most rear drive cars have a 1 to 1, 4th or 5th gear which means that the power path goes directly through the mainshaft of the transmission. The only losses here are bearing drag which is less than 0.5% and the viscous drag of the gears running through the oil which is about 1% with hot oil. Indeed, published data indicates a transmission efficiency of 98 to 98.5% for conventional transmissions in 4th gear.
Losses within the driveshaft account for about 0.5% if they are properly aligned, balanced and with fresh U-joints.
Differential losses in the commonly used Hypoid type gearset is in the order of 6 to 10%.
The worst scenario case for a rear drive setup is on the order of 12.5% in 4th gear, not the 20 -25% often published. If 25% was being lost in the drivetrain, the oil would boil in the differential housing in short order and aluminum transmission cases would fatigue and break from the temperatures generated. On a 200 hp engine, something on the order of 37,000 watts would have to be dissipated out of the transmission and differential housings. Obviously, this is not the case.
Transverse, front drive transaxles usually have no direct lockup gears and no 1 to 1 ratio, however, since the torque path is never turned 90 degrees as in the rear drive setup and efficient helical gears are usually employed for the final drive set, losses are more on the order of 6 to 9 percent in the upper ratios.
Tire pressure and wheel alignment can have very significant effects on losses at the rollers. Tire pressures should be set the same between each test. Tire rolling resistance varies inversely with speed, another factor not taken into account by most chassis dynos when applying phantom flywheel hp formulas.
why do you continually post this dyno article that completely misses the point of rotaional inertial losses?
01-13-2006, 02:12 AM
#630
The Professor
Originally Posted by olddragger
One thing I have noticed-- and my interpretation skills may be untuned---but this car has a high rolling resistance(stock tires). In neutral rolling down the hill in front of my home the car doesnt gain the speed one would think. Comparing the 8 to my sons Ford ranger p/u and, to my daughters volvo(i know front wheel drive but this is just rolling resistance--no power) it gains much less speed than theirs. I know I have wider tires but I dont think that accounts for it all. Tight can be good(lol) but sometimes it can rob power. Food for thought?
Olddragger
Olddragger
01-13-2006, 06:52 AM
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Originally Posted by rotarygod
I posted it to show that a 25% drivetrain loss is complete bs.
01-13-2006, 12:33 PM
#634
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NEMESIS8:Hey, look what CERAMICSEAL said over at RX7Club
Quote:
Originally Posted by CERAMICSEAL
The re-mans are $2800 plus core. The core charge is $1000. They've been known to make as much as 265hp to the flywheel with the right management and the right seals. Pretty incredible for normally aspirated with smooth idle.
In this thread: http://www.rx7club.com/showthread.php?t=496533
So whats 265 at the flywheel in RWHP????
Quote:
Originally Posted by CERAMICSEAL
The re-mans are $2800 plus core. The core charge is $1000. They've been known to make as much as 265hp to the flywheel with the right management and the right seals. Pretty incredible for normally aspirated with smooth idle.
In this thread: http://www.rx7club.com/showthread.php?t=496533
So whats 265 at the flywheel in RWHP????
01-25-2006, 04:25 PM
#638
I don't know why you guys are arguing about drivetrain losses, that was all covered earlier, I posted a statistical analysis graph of over 400 makes/models that were tested for the difference in their advertised vs rear wheel output AS TESTED ON A HUB DYNO, not a BS drum dyno. The bell curve peak differences were 9% on HP and 7% on torque, some were higher and some were lower, but they concluded that anything greater than 15% was inaccurately advertised output by the manufacturer. They also discussed real world losses for trans gears and R&P gears.
https://www.rx8club.com/showpost.php...&postcount=588
Please stop rehashing the same BS over and over again, this thread is too difficult to follow as it is.
Getting back on track, the Italian Cup RX-8's are putting 270hp to the flywheel with intake, exhaust, and ECU mods, this was on US equivalent 95 octane fuel
https://www.rx8club.com/showpost.php...&postcount=588
Please stop rehashing the same BS over and over again, this thread is too difficult to follow as it is.
Getting back on track, the Italian Cup RX-8's are putting 270hp to the flywheel with intake, exhaust, and ECU mods, this was on US equivalent 95 octane fuel
Last edited by TeamRX8; 01-25-2006 at 04:29 PM.
01-25-2006, 06:29 PM
#639
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Originally Posted by TeamRX8
I don't know why you guys are arguing about drivetrain losses, that was all covered earlier, I posted a statistical analysis graph of over 400 makes/models that were tested for the difference in their advertised vs rear wheel output AS TESTED ON A HUB DYNO, not a BS drum dyno. The bell curve peak differences were 9% on HP and 7% on torque, some were higher and some were lower, but they concluded that anything greater than 15% was inaccurately advertised output by the manufacturer. They also discussed real world losses for trans gears and R&P gears.
https://www.rx8club.com/showpost.php...&postcount=588
Please stop rehashing the same BS over and over again, this thread is too difficult to follow as it is.
Getting back on track, the Italian Cup RX-8's are putting 270hp to the flywheel with intake, exhaust, and ECU mods, this was on US equivalent 95 octane fuel
https://www.rx8club.com/showpost.php...&postcount=588
Please stop rehashing the same BS over and over again, this thread is too difficult to follow as it is.
Getting back on track, the Italian Cup RX-8's are putting 270hp to the flywheel with intake, exhaust, and ECU mods, this was on US equivalent 95 octane fuel
I'd like to know their dyno testing method that associated with that graph.
I would suspect that since that is from a tranny manufacturer, they run the dyno up and hold it stead every XXX RPMs for 10-15 seconds, records the steady state power, and then step the RPMs progressively up - this makes the losses associated with inertia go to 0 during the steady state period because the drivetrain is no longer accelerating, and hence they can filter out inertial losses to narrow the losses down to friction and their tranny.
If that is the case that graph no longer makes sense on a chassis dyno where the drivetrain is constantly accelerating (based on the setup of the dyno in some cases).
01-25-2006, 06:46 PM
#640
I only ever did this once and it was a long time ago. My engine made 335 on the engine dyno and 290 on the chassis dyno. That's 13%. All I have to offer.
Oh, it was a solid rear drive with staight through trans in high gear. Wait.....
We dyno'ed it in third gear so it was indirect.
Had to do that as the car was geared for Bonniville.
Oh, it was a solid rear drive with staight through trans in high gear. Wait.....
We dyno'ed it in third gear so it was indirect.
Had to do that as the car was geared for Bonniville.
01-25-2006, 07:12 PM
#641
Administrator
roto the pdf he linked to in his post explains it. BUT it still doesnt settle anything since they didnt test the engines.
i dod agree with it that the dynapack attached to the hub type dyno is much better than the rolling road type.
i dod agree with it that the dynapack attached to the hub type dyno is much better than the rolling road type.
01-25-2006, 07:21 PM
#642
Administrator
went to my bookmarks for this article- its my favorite when it comes to dyno discussions
http://www.wrc-tech.co.uk/services-rolling-road-faq.htm
best part
http://www.wrc-tech.co.uk/services-rolling-road-faq.htm
best part
Is it possible to measure the true transmission loss of a car?
Yes - only one - by measuring the flywheel power on an accurate engine dyno, the wheel power on an accurate chassis dyno and taking one away from the other. There is no way of finding out the true transmission loss just by measuring the power at the wheels.
Yes - only one - by measuring the flywheel power on an accurate engine dyno, the wheel power on an accurate chassis dyno and taking one away from the other. There is no way of finding out the true transmission loss just by measuring the power at the wheels.
01-25-2006, 11:57 PM
#643
not entirely true, there is another method as described on the Roto-Test site; they install a special strain gauge mechanism in the drivetrain. This can measure the actual loss all in the same dyno pull, quite accurately too. However, you are correct in that they never actually dyno'd the engines themselves, it is simply a statistical analysis of the difference between the manufacturers claimed engine output and actual rear wheel measurement, as I stated.
For those who may not understand the difference between a hub dyno and a drum roller dyno, the dyno's that RotoTest and DynaPack attach to the rear hubs and measure rear wheel output directly is the same type of dyno you measure engine output directly with, just that there are two of them, one on each drive wheel (or four for AWD).
For those who may not understand the difference between a hub dyno and a drum roller dyno, the dyno's that RotoTest and DynaPack attach to the rear hubs and measure rear wheel output directly is the same type of dyno you measure engine output directly with, just that there are two of them, one on each drive wheel (or four for AWD).
Last edited by TeamRX8; 01-25-2006 at 11:59 PM.
01-26-2006, 07:12 AM
#644
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Originally Posted by zoom44
roto the pdf he linked to in his post explains it. BUT it still doesnt settle anything since they didnt test the engines.
i dod agree with it that the dynapack attached to the hub type dyno is much better than the rolling road type.
i dod agree with it that the dynapack attached to the hub type dyno is much better than the rolling road type.
Rototest is probably the best available to the general public. On a rototest you define the amount of time it allows the drivetrain to go from idle rpms to redline. Inertial losses can be completely controlled on these things because of this - and in the more scientific testing world you actually step up the rpms in small increments to create no inertial losses (as I have done testing engines and gearboxes).
In fact, if you have a good enough cooling system you can let the engine spin up in 20 sec, find the rpm with peak power, then crank up the resistance to hold the engine steady at the peak power and watch as the dyno indicate you slowly "gain" 6-8hp. I've done it a number of times in the testing labs and it always works as you make inertial losses approach zero.
These results are NOT comparable to a typical roller chassis dyno you'll find down the street that simply measures how fast you can spin the roller.
01-26-2006, 06:32 PM
#647
Purveyor of fine bass
Originally Posted by BlueRenesis82
so, this interceptor for n/a cars......benefits?
01-27-2006, 03:51 PM
#649
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Guys,
Any update on the Interceptor? Last I heard it was being perfected but I tried to read into some of the posts for updates and after 2 pages of drive train loss discussion I got burnt out.
Just wondering what the price will be and approx. when it will come out. I already saw the dyno and it looks good. Thats brings another question...Was that dyno with the ECU only or did the car have additional upgrades like a midpipe?
Thanks!
Any update on the Interceptor? Last I heard it was being perfected but I tried to read into some of the posts for updates and after 2 pages of drive train loss discussion I got burnt out.
Just wondering what the price will be and approx. when it will come out. I already saw the dyno and it looks good. Thats brings another question...Was that dyno with the ECU only or did the car have additional upgrades like a midpipe?
Thanks!
01-27-2006, 04:06 PM
#650
Go Texas Longhorns!
Talked with Scott today, both the NA and FI units are finished and ready for production. He is in the process of getting units together, I expect him to post some more info soon.
In addition, Scott is working on some other interesting products that will be coming soon. He's really taking his time to make sure that what he sells works right the first time.
In addition, Scott is working on some other interesting products that will be coming soon. He's really taking his time to make sure that what he sells works right the first time.