New Turbo Kit!
05-25-2006, 12:08 PM
#151
RX8 and a Truk....
Originally Posted by MadDog
Have to disagree with you there. If frictional losses were a constant, then we'd have to dyno negative HP down at the low end where the engine actually makes less than this magical 40hp, right?
Obviously, the frictional losses are not a constant. Frictional forces are proportional to velocity terms. In our case, force is in units of torque, and angular velocity is RPM.
T_friction=(some constant)*Angular Velocity
If you want to see what effect that has on HP measured, its
HP_lost_due_to_friction=T_friction*(constant)*RPM/5250
Its obvious that HP lost IS a percentage of HP made by the engine, NOT a constant.
Obviously, the frictional losses are not a constant. Frictional forces are proportional to velocity terms. In our case, force is in units of torque, and angular velocity is RPM.
T_friction=(some constant)*Angular Velocity
If you want to see what effect that has on HP measured, its
HP_lost_due_to_friction=T_friction*(constant)*RPM/5250
Its obvious that HP lost IS a percentage of HP made by the engine, NOT a constant.
Miatas universally lose about 26hp from flywheel to wheel. tis not a constant NOR a percentage...it's sort of both.
Great thread on the subject here:
http://forum.miata.net/vb/showthread...hlight=dynojet
05-25-2006, 12:09 PM
#152
Originally Posted by rotarygod
Remember what Richard is so fond of saying. "When the results don't match the theory get a new theory". Mine fits.
We all know how valuable those are for showing absolute numbers.
I'd be far more willing to accept that if I saw a plot before the FI on the same car on the same dyno. Without that, I am forced to conclude that those numbers are a fabrication (not necessarily intentional, BTW - I'm not calling Scott a liar).
BTW - that stuff is no theory. There is always a gray area because it usually takes more than the optimum to produce the final result, but the final power capacity of air and fuel is absolute. I tried to optimize my numbers to arrive at your accepted result.
05-25-2006, 12:17 PM
#153
Registered
Actually I do have to concede one thing and go back and say you are correct on one thing. I had to think about it a little harder. Yes a dyno has larger losses the faster you try to spin it up. I'm not quite sure what I was thinking on that one so yes I need to correct that.
However, the Renesis is far more capable in the power department than anyone thinks it is. We are only just now realizing it's true potential and we still probably haven't seen it all yet. It is very possible to hit 300 rwhp at 5 psi. This is not hard to comprehend at all. It makes more power than the 13B and yet people routinely dyno over 400 rwhp at 15 psi of boost all the time with some hitting it as low as 13.5 psi. You can't go back and tell everyone out there who has done it over the past couple of decades that they are wrong. Scott did 300 rwhp at 5 psi and 350 at 12.5 psi. That's not uncommon for a rotary and perfectly inline with what people have been doing for years. If everyone's numbers agree and the only thing that doesn't is your theory, get a new one. It's off.
However, the Renesis is far more capable in the power department than anyone thinks it is. We are only just now realizing it's true potential and we still probably haven't seen it all yet. It is very possible to hit 300 rwhp at 5 psi. This is not hard to comprehend at all. It makes more power than the 13B and yet people routinely dyno over 400 rwhp at 15 psi of boost all the time with some hitting it as low as 13.5 psi. You can't go back and tell everyone out there who has done it over the past couple of decades that they are wrong. Scott did 300 rwhp at 5 psi and 350 at 12.5 psi. That's not uncommon for a rotary and perfectly inline with what people have been doing for years. If everyone's numbers agree and the only thing that doesn't is your theory, get a new one. It's off.
05-25-2006, 01:07 PM
#154
Originally Posted by rotarygod
It's off.
400 RWHP at 15 PSI? That is a PR of over 2.
What is the typical RWHP number on an FD at its stated 255 engine HP?
Do the math! You are still in fantasy land if you think an FD is going to put down 300 RWHP at a PR of 1.3. Hell, its OEM tuning is hotter than that and the RWHP is barely 2/3 of this claim.
I am not disagreeing that the MSP has potential. I think I proved that almost two years ago. But it will not defy physics.
I can see a RWHP number of 260 at a PR of 1.3 (even that would be incredible), but not 300. I'm putting down about 280 at a PR of 1.6 with pretty modest tuning.
I'll post IM temps later today so we can get the ball rolling on the whole comp. eff. thing. I'm sure you will all be suprised. I know I am, but I was expecting the worst. It still won't make up for fantasy numbers.
05-25-2006, 01:22 PM
#155
Registered
How much power could an FD engine do without the turbos? It would not hit 200 hp. An FD WITH turbos is rated at 255 rwhp at 9 psi of boost. So what? What's that have to do with anything? Stop basing your calculations off of what engines come with and look to what they can do. How much an FD puts down stock and at what pressure is completely irrelevant. Based on what you are telling me, it's impossible to hit 400 rwhp on an FD engine that can only make less than 200 hp sans turbos at a boost pressure of 14.7 psi. You need to look at the engine without turbos before you can say what it's potential is with them. Yet somehow at the same time you are saying the 3rd gen can hit this number at this boost level. It can. It's been done. See the issue? You're numbers are somehow off and it's obvious how. There is no defying physics about any of it.
05-25-2006, 01:24 PM
#156
Ugh. OK, how much air and fuel is an FD ingesting to make 400 RWHP (or 300 for that matter)?
Care to hazzard a guess?
BTW - Let me make myself perfectly clear. I am NOT saying it isn't possible to get that kind of power out of a Renesis. What I AM saying is that it isn't possible with that little air and that little fuel.
Care to hazzard a guess?
BTW - Let me make myself perfectly clear. I am NOT saying it isn't possible to get that kind of power out of a Renesis. What I AM saying is that it isn't possible with that little air and that little fuel.
Last edited by MazdaManiac; 05-25-2006 at 01:29 PM.
05-25-2006, 01:32 PM
#157
At this point, I don't really follow the discussion. Assuming nobody is declaring the 5 psi Dyno utterly fake, the question is not if the car made 300 whp, but how. It wasn't running 5 PSI on the dot, it was running a nominal 5 psi. Maybe it was a high 5. Also, wouldn't you consider what other mods the car has besides just an intake pressure boost? A test vehicle doesn't always begin bone stock. Whats the highest NA WHP people have made on an RX-8 with stock rotors/housings? If the dyno increases in friction as you run it faster, does that somehow mean a 9k rpm, 5th gear in one car has more drag instantaneously than another rx-8 at 9k in 5th?
05-25-2006, 01:41 PM
#158
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^that's why MM wanted to see a before and after sheet done on the same car. Then all the unknowns are taken into account and you can base the increase in power on the additional air/fuel alone.
05-25-2006, 01:46 PM
#159
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i made 306 whp @ 6 psi with very conservative tuning on a very small streetport in an rx7 with a td06. same hp @ 5psi is totally realistic from the renesis. i don't know what turbo scott's using in the kit, but with all the times i've talked to him, i get the impression he doesn't bullshit.
turbos that work for the renesis aren't the same as turbos that work for an older engine, although they will have overlapping flow rates. for this motor, we'd be looking for a turbo that is efficient at very low boost levels (<12psi), whereas your typical 35r, t66, etc that works for an rx7 doesn't even come alive until then.
so maybe the turbo has less hp potential, but is more efficient in the low boost levels--right where the renesis guys need it.
turbos that work for the renesis aren't the same as turbos that work for an older engine, although they will have overlapping flow rates. for this motor, we'd be looking for a turbo that is efficient at very low boost levels (<12psi), whereas your typical 35r, t66, etc that works for an rx7 doesn't even come alive until then.
so maybe the turbo has less hp potential, but is more efficient in the low boost levels--right where the renesis guys need it.
05-25-2006, 02:16 PM
#160
Administrator
Originally Posted by dmp
Miatas universally lose about 26hp from flywheel to wheel. tis not a constant NOR a percentage...it's sort of both.
Great thread on the subject here:
http://forum.miata.net/vb/showthread...hlight=dynojet
Great thread on the subject here:
http://forum.miata.net/vb/showthread...hlight=dynojet
dont make me start with you again
05-25-2006, 02:43 PM
#161
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Originally Posted by rotarygod
An FD WITH turbos is rated at 255 rwhp at 9 psi of boost.
05-25-2006, 02:46 PM
#162
Originally Posted by Blue87Sport
Not to anger the gods, but a stock FD makes 255 hp at the crank, not the wheels. According to the FAQ on the RX-7 club http://www.rx7club.com/showthread.php?t=68640 it puts around 220 to the wheels on a Dynojet.
Most stock FDs were putting about 205 - 215 to the wheels for the most part.
05-25-2006, 03:18 PM
#163
RX8 and a Truk....
Originally Posted by zoom44
dont make me start with you again
lmao
Actually, I'm remembering Mustang GTs of yore...220hp, and they'd put down about 170-175whp. I figure my car's 197whp is a pretty good indication that Mazda may be 'close' with 232hp rating.
05-25-2006, 04:25 PM
#167
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with so many unknowns in this equation, I don't think any theory is going to explain anything. Dyno's may not be the best, but the numbers do not lie (given it is correctly calibrated and used, which knowing Scott, it was). we do not know: flow rates of the turbo or even what turbo it is (actually I do, but I'm not going to spoil any suprises), conditions the dyno pulls were done in, true potential of the NA renesis, true effect of bolt-on modifications under NA and under FI. MM makes a good point with the phyics side of it, but if reality says otherwise you have to consider other variables.
Why is so had to just believe what was said? I don't see any incentives to lie about the numbers, he's already miles ahead of anything else on the market.
Why is so had to just believe what was said? I don't see any incentives to lie about the numbers, he's already miles ahead of anything else on the market.
05-25-2006, 04:50 PM
#168
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Originally Posted by guitarjunkie28
and the ls1 is rated at 320 hp, but somehow puts 310+ whp down in stock form.
gm is less optimistic with their ratings.
gm is less optimistic with their ratings.
05-25-2006, 05:53 PM
#174
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Originally Posted by maxxdamigz
There are 2 sources of losses: Inertial and frictional. Depending on drive train components in a system, the share between these can probably be anything.
Frictional losses depend mostly on speed. As rg stated, pretty much, an engine driving a dyno from a simulated 30 mph to a simulated 100 mph will have the same speed and, therefore, frictional losses at either end.
Inertial losses will rise with horsepower. Accelerating the drivetrain its self between 2 speeds is a power loss. A 400 hp engine will accelerate faster and dump energy into that motion faster than a 200 hp engine. This is why a dyno pull in first gear will show a greater gain from a LWFW than a 4rth gear pull.
Now, I can't really say what the balance between the 2 is in the RX-8. I have no idea. Maybe a stock engine loses 40 hp and a 400 hp one loses 50. There is a case to be made for both types of losses so I should think you are both right to a certain extent.
Frictional losses depend mostly on speed. As rg stated, pretty much, an engine driving a dyno from a simulated 30 mph to a simulated 100 mph will have the same speed and, therefore, frictional losses at either end.
Inertial losses will rise with horsepower. Accelerating the drivetrain its self between 2 speeds is a power loss. A 400 hp engine will accelerate faster and dump energy into that motion faster than a 200 hp engine. This is why a dyno pull in first gear will show a greater gain from a LWFW than a 4rth gear pull.
Now, I can't really say what the balance between the 2 is in the RX-8. I have no idea. Maybe a stock engine loses 40 hp and a 400 hp one loses 50. There is a case to be made for both types of losses so I should think you are both right to a certain extent.
correct, and to add to that the inertial losses on a chassis dyno vary tremendously between differnt type of dynos....
- Some dyno's produce a constant braking force which means the more power your car has, the faster it will spin up on the dyno and produce more inertial losses. These dyno's can be tricky when you try to compare products because your shooting yourself in the foot with drivetrain losses when adding power (but this is the case in real life....)
- some dyno's produce a constant rate of acceleration no matter what the hp of the car is... so you dyno the car NA and add a 100hp and come back, you will have the same amount of power lost in the drivetrain show up.
- some dyno's can actually produce enough force to hold speed constant at varying rpms levels - so this way you have no intertial losses showing up at all...
05-25-2006, 06:55 PM
#175
Registered
Originally Posted by MazdaManiac
Nah, I already had one of those in the '80s.
Having detroit iron (aluminum) under the hood of a rice grinder just means I get to alienate myself from both sides of the argument.
Having detroit iron (aluminum) under the hood of a rice grinder just means I get to alienate myself from both sides of the argument.