eaton, according to car and driver.

300bhp/ton · Jun 13, 2005

ttown said:
People been using the 15% figure since before you and I were born son, grow up. It's as good as any figure you can give. Which is a bunch of BS.

just because people have been using it doesn't make it CORRECT num nuts. Come on people used to beleive smoking was not harmful until science proved it could be.

In fact it is even more proof that its flawed as older cars 60's & 70's tend to loose more through the drive train than the modern counter parts. So go figure

The only reason people don't like hearing it, is beacause people like you just get upset when they find out their car isn't as powerful as they hoped. However hoping it produces more power and using inaccurate methods of calculating it won't make it any faster at the track!

fullsagd · Jun 13, 2005

300bhp/ton said:
You are so dum!

1 metric HP has a different value to 1 Imperial HP, it is that simple.

QUOTE]

...."dum"....check out the occupation, i'll add that i am a power and mechanical engineering teaching assistant at the local college town in my spare time. 1 metric horsepower...if you are talking kW's then of course there will be a different value, there are different root values used. and there is a metric and international horsepower, but the conversion is "1 horsepower [metric] = 0.9863201 horsepower [international]" so the conversion factor is negligable. either you aren't explaining yourself clearly enough or YOU don't have any education this field and any idea what you are talking about, which seems more than likely given all the mistakes you have made in terminology.

300bhp/ton · Jun 13, 2005

fullsagd said:
300bhp/ton said:

You are so dum!

1 metric HP has a different value to 1 Imperial HP, it is that simple.

QUOTE]

...."dum"....check out the occupation, i'll add that i am a power and mechanical engineering teaching assistant at the local college town in my spare time. 1 metric horsepower...if you are talking kW's then of course there will be a different value, there are different root values used. and there is a metric and international horsepower, but the conversion is "1 horsepower [metric] = 0.9863201 horsepower [international]" so the conversion factor is negligable. either you aren't explaining yourself clearly enough or YOU don't have any education this field and any idea what you are talking about, which seems more than likely given all the mistakes you have made in terminology.

Click to expand...

mistakes - almost certainly

But it still doesn't prove the 03/4 Cobra's had way more power than listed.

I guess what we need to do is get a magazine to either buy a crate motor or rip a stock one out of a car and slap it on an engine dyno and really see what it was making in SAE Net bhp terms.

I think it was hot rod magazine did this with a Corvette Z06 (Ls6 5.7) engine. It was (as I'm sure you know) rated @ 405bhp SAE Net by Chevy. They dyno'd it at 417bhp and once the correction factor was added it came in at about 410-412 (can't remeber which) bhp SAE Net.

I just find it interesting, and in all reality there are so many possibilities. Even more so with a blown engine, as I guess you could be really sneaky and rate the engine power minus the loss of power by the blower, although I think this is the main area where the SAE standards try and prevent mis leading engine outputs.

In short there is no way to know without putting a stock engine on an engine dyno.

Not sure of the setup drivetrain wise but some the earlier non s/c Cobra's had 320bhp SAE Net, if you work on the 15% drivetrain loss theory they should be loosing 48bhp. If the s/c Cobra's have the same drivetrain setup would the drivetrian really be using double the power to power it (360rwhp and a claim of 425bhp SAE Net leaves 85hp lost in the drive train?).

The big thing with the 15% rule is, if your car dyno's say 482rwhp then that would mean 567bhp crank. Which is impressive, but maybe a little to impressive for a road going 4.6 V8.

Where as if you assume the amount lost is fairly constant (assuming the drivetrain has remained stock) and only increases at a lower rate, so at the level of tune it may well be only loosing 40 or so hp, giving a slightly less impressive 522bhp SAE Net.

I really don't know the answers. Just an alternative theory which also has evidance to support it.

Some come guys and girls lets start badgering a magazine to put a s/c Cobra engine on a engine dyno and rate it at SAE Net standards so we can all find out how much power it has.

fzust · Jun 14, 2005

The important thing is that with the Eaton the low $ horsepower gains are much more limited than a twin screw. The Eaton heats the air far more than the twinscrew with a larger pulley. MM&FF was thinking that with a twin-screw, larger pulley, exhaust, intake and some port work on the heads, we could be looking at 700RWHP. That will not happen with the Eaton. For real power, best to rip it off and get the KB.

Chupacabras · Jun 14, 2005

Cobra R's were much lighter. So if they are running similar performance numbers, then the 03/04's must have more HP. Mine SAE dynod at 371 at the wheels which seems to be around the average number of all the 03/04's that have been dynod stock.

Don't really need to be a math wiz or a mech engineer to figure it out....

Ken

ttown · Jun 14, 2005

Chupacabras said:
Cobra R's were much lighter. So if they are running similar performance numbers, then the 03/04's must have more HP. Mine SAE dynod at 371 at the wheels which seems to be around the average number of all the 03/04's that have been dynod stock.

Don't really need to be a math wiz or a mech engineer to figure it out....

Ken

You can't argure with those guys from England they know much more about our American cars than us dum Americans hanging out with our Mustang Clubs at the dynos.

COBRA90GT · Jun 15, 2005

Ok guys, knock it off...

Debate is fine, but keep the personal attacks off the message board. If you wish to continue the insults, feel free to do via PM or e-mail with one another, but NOT here.

Thanks for your cooperation.

Gearbanger 101 · Oct 31, 2005

300bhp/ton said:
Yeah but reading between the lines on all that I've seen so far I would say that is marketing BS

The Whipple was only running 8-8.5psi

The Eaton is @ 10psi and there could be other changes too (Tune & cam specs). Like for like basis the twin screw blower will produce more power & torque than a roots ANYWHERE in the rpm range.

As per usual, I disagree with you on this point, but what else is new, huh?

The Whipple 2300 used on the GT-40 is a 2.3-liter blower, the M122 being used on the GT500 is slightly under 2.0-liters and the M112 used with the Cobra is only 1.83-liters by comparison. It seems to me, that the performance and efficiency difference between the bunch, is mostly related to their difference in capable volume, not in their difference in design.

I have yet to see anyone from the "twin screw" camp definitevley prove that a twin screw with all things being equal will outperform a roots based blower at anything other than peek levels.

EDIT
Oops...sorry for bringing this one back from the dead guys, I was doing a search for crank pulleys and forgot that I was in the archives when I answered this one.

Trublu01 · Nov 7, 2005

Who gives a crap about anything but peak? Especially with roots style blowers. They are low RPM performers for the most part anyway. It is a fact that a twin screw does out perform a single screw. If it didn't, there wouldn't be one!

Gearbanger 101 · Nov 7, 2005

Trublu01 said:
Who gives a crap about anything but peak? Especially with roots style blowers. They are low RPM performers for the most part anyway. It is a fact that a twin screw does out perform a single screw. If it didn't, there wouldn't be one!

If nobody cared about anything but peak boost levels, then we'd all be driving around with Centrifugal superchargers under the hood, since we all know that they rule the roost from that respect. If by outperforming a Roots blower with a Twin screw, you refer to peak numbers, then you are correct again, but the Twin Screw guys still haven't got all the angles covered at lower boost levels. Twin screws run hotter at lower boost levels than any other blower, Roots style included and perform less efficiently at that level than the Roots style does........THAT IS A FACT! Not a problem if you're always running around with your foot to the floor, but if you've got an ACT gauge and spend a lot of time below 6psi under moderate driving conditions, you'll see in a hurry why Twin Screws haven't been considered "a better built mouse trap" just yet.

......and by the way, WTF is a single screw?

Trublu01 · Nov 7, 2005

A roots type/style supercharger is an Eaton, Whipple, KB, etc. A single screw would be what Eaton puts out and twin screw is what Whipple and KB put out. Who the hell drives a 16+ psi car around under 6psi?

Gearbanger 101 · Nov 7, 2005

Trublu01 said:
A roots type/style supercharger is an Eaton, Whipple, KB, etc. A single screw would be what Eaton puts out and twin screw is what Whipple and KB put out. Who the hell drives a 16+ psi car around under 6psi?

No offence Sprayman, but you should stick to the Nitrous, because it's quite obvious that you don't have the slightest clue what you're talking about! Eaton, Whipple and KB are all "Positive Displacement" blowers, this much is true, but only Whipple and Kenne Bell utilize "Screw" Compressors. Eaton blowers do not utilize "Screw Compressors", they work with a "Lobe" type compressor that more or less paddle air back and forth within the housing until discharge, where the majority of it's compression takes place within the intake system like a Centrifugal. Screw compressors use dual intermeshing units that resemble cork screws, hence the term "Scew Copressor", that compress the air directly between one and other, within the blower housing itself. The two blowers may accomplish the same over all results, but their methods on doing so are as different as apples and oranges.

As for who drives a car that peeks at 16psi around under 6pounds of boost? Well….everyone. You can’t always have your foot in the oil pan under wide open throttle, which is the only time you’re actually going to see those numbers anyway. Under partial load, the average blower car spends more time below or around 6-8psi than any other level of boost, which is why it’s as important to keep air temps under control as much at that level, than it is at max.

Trublu01 · Nov 8, 2005

No argument here, however after some quick research, http://www.coloradocobras.com/whipple/superchargers/twin-screw-superchargers.html

300bhp/ton · Nov 8, 2005

Gearbanger 101 said:
The two blowers may accomplish the same over all results, but their methods on doing so are as different as apples and oranges.

Well they don't really produce the same results. The TS will outperform the Roots. But yes their methods are very different.

Gearbanger 101 said:
As for who drives a car that peeks at 16psi around under 6pounds of boost? Well….everyone. You can’t always have your foot in the oil pan under wide open throttle, which is the only time you’re actually going to see those numbers anyway. Under partial load, the average blower car spends more time below or around 6-8psi than any other level of boost, which is why it’s as important to keep air temps under control as much at that level, than it is at max.

I agree that you don't drive at WOT all the time, but it is for this reason that the TS can produce another trump card, well kinda.

You claim that in these low boost/load periods the intake temp from a TS is higher than that of a Roots. Well if you are only at light throttle then you evidently are not wanting to move quickly. And as we all know hotter air is better for fuel economy. So the TS can match the Roots for low end grunt produce similar high rpm boost to a centrifugal and be more economical in low load conditions than an Eaton?

BTW do you have any data/references for the IAT for TS and Roots blowers for a directly comparative test at all? Cheers.

Gearbanger 101 · Nov 8, 2005

300bhp/ton said:
You claim that in these low boost/load periods the intake temp from a TS is higher than that of a Roots. Well if you are only at light throttle then you evidently are not wanting to move quickly. And as we all know hotter air is better for fuel economy. So the TS can match the Roots for low end grunt produce similar high rpm boost to a centrifugal and be more economical in low load conditions than an Eaton?

BTW do you have any data/references for the IAT for TS and Roots blowers for a directly comparative test at all? Cheers.

You don't have to be "too the floor" so to speak to want to move quickly with a blower car. Often when doing a lot of highway driving in hilly terrain, it's nice not to have to shift out of overdrive in order to climb a hill, or leisurely pass a car. Or even with brisk in town driving.....these are all conditions where you would see lower boost levels that do not favor the Screw blower. It may very well be insignificant if you're on and off the throttle, or stuffing it right into the floor boards where the gauge sweeps right on up to max PSI.....but aside from these conditions, it would pose a factor none the less.

As for better fuel economy because of a warmer air charge....that's kind of a moot point, since all blowers produce hot air regardless of their design. The negative drawback to this though, is that the hotter the air charge is going to send a signal to the ECU to pull timing to compensate. This is going to make the car lazier which will require more throttle to overcome......harming gas mileage in the process. In non boosted situations, an Eaton consumes less than 1/3 of a horsepower (or at least my M90 does) and I would assume the same holds true for a Twin Screw

As for data on comparisons between the two, I suppose I could take a couple of hours searching around for some, but there are really too many factors to take into account for it to be a completely bias comparison at any account. First off, you rarely often see ACT measured at the blower itself, without the rest of the intake system skewing the results. I often wonder if this is one of the reason you don't see Centrifugal chargers with stock intake cars making as high of numbers as positive displacement blowers at the same level of boost. Positive Displacement kits for the most part often benefit from short generous runners that boast cavernous strait runners and offer superior breathing ability, since there is no need to take into account a loss of bottom end torque when running the positive displacement blower. As such, you don't see as high of numbers on the boost gauge, since less of it is getting backed up within the intake system like they do with the longer, smaller runners (in order to utilize bottom end torque) like those seen with centrifugal applications.

Secondly, you've got the physical size difference between each blower. My M90 is smaller than a KB 1.7 and won't support any where near the volume of air, regardless of it's design. An M112 is larger and will support the volume, but unfortunately none of the blower manufacturers that build 2V kits (Roush, Saleen, FRPP) utilize a manifold to match the flow potential of the admittedly better design of the Kenne Bell, which throws a wrench into things again. Then you've got the 2.2KB which is much larger than the M112 and puts it in the same situation than the M90 was in with the 1.7KB.

The only fair comparison between the two comes right down to thermal dynamics of it. The bigger the blower, the higher the ACT's are at lower boost levels because the larger blowers are built to run their most efficient at higher blower RPM (Boost levels). A screw compressor is always compressing the air charge. Whether you're at idle, or at WOT. Yes, KB utilizes a bypass valve in their system to ensure that you're not always driving pressurized air into the intake manifold, but whether it's ingesting it, or not the air charge is always heated, just the same. The Screw compressor was designed with upper blower RPM in mind. The Screws provide a better sealing surface to resist "leak down" which creates turbulence and friction within the housing that causes an Eaton to overheat when blower RPM increases beyond it’s capacity. For this reason alone, the Twin Screw takes over in the upper blower RPM ranges long after the Eaton has signed off, but in order to do this, they still have to take the hit someplace else in it’s efficiency range....just like every blower does and that place in the lower levels. It may not be as big of a drawback or as noticeable in comparison to a Centrifugal blower, which isn't producing near the volume of air that the Twin Screw does at lower RPM regardless of the temperature charge and therefore takes a back seat in the low end torque department, but it does experience an elevated temperature charge just the same.

The Eaton on the other hand as I'm sure you know utilizes a set of lobes, which more or less paddles the air back and forth within the housing until such time as it's needed. At which point the bypass valve begins to close causing it to pressurize the intake. The difference in this case though, is that the air is not compressed within the blower housing itself as it is with the Twin Screw and as such, remains cooler at those lower levels by comparison.

Do you agree with this logic, or does your opinion differ?

1994Vobra · Nov 30, 2005

300bhp/ton said:
You are so dum!

1 metric HP has a different value to 1 Imperial HP, it is that simple.

Same goes for wieghts and measures, 1 US gallon is smaller than 1 Imperial gallon.

1 Imperial ton weighs less than 1 metric tonne.

1bhp SAE Net has a different value to 1PS

If you really don't get then I wash my hands of you!

Where are these Cobra's making 380rwhp stock NEVER seen one.

360rwhp - yes. but 360 what. It won't be SAE Net hp that has been measured. And you are also assuming the STUPID 15% rule is accurate.

People seriously can't really be this stupid. I mean you are using a keyboard and mouse to access this site

If you really beleive that 03/4 Cobra's produced 425+bhp then they would have to be one of the most dissapointing performance cars of the last few years, as they should be a lot faster than they are, I me come on the Cobra R will post the same performance figures stock for stock. How much HP did it have - - - is that 385bhp I hear. Almost identical to a stock Cobra, so again its no wonder they produce similar ET's.

Wow,
This guy is a know it all who obviously knows alot about nothing to do with Mustang Cobras

This is especially entertaining..

360rwhp - yes. but 360 what. It won't be SAE Net hp that has been measured.

300bhp/ton · Nov 30, 2005

Bring back an old thread, hay???

1994Vobra said:
Wow,
This guy is a know it all who obviously knows alot about nothing to do with Mustang Cobras

This is especially entertaining..

Mustangs, Cobra or otherwise still follow the same laws of physics as everything else does.

Very few engines are really underatted, it's just most people don't have a clue about how different meausres are derived. Sad but true.

I even have my suspisions about some of the Fbody claims (and I own one of them!!!!).

Did you know that you can dyno the SAME car on a Dynojet and then on a Mustang Dyno and see upto 20rwhp difference in the results, straight off.

This is because the Mustang Dyno is load bearing and the Dynojet isn't. It does NOT however mean that the car was producing more power on the Dynojet, just that it was derived differently.

And remember most dyno's rate in STD not SAE. So in most cases (without worrying about how it does it) just knock 10rwhp off.

So if a car made 380rwhp STD on a Dynojet. It would be nearer to 350-355rwhp SAE on a Mustang Dyno rated in SAE. This hasn't even taken into account any of the local and atmospheric conditons which should also be corrected for by calculations.

See how easy numbers get mixed up. If a Cobra really is making 350rwhp once every thing is accounted for, then ~390bhp SAE Net at the engine is probably spot on.

Of course you could re-rate the manufactures claimed figure to STD which would probably put it at over 400bhp, but it wouldn't any longer be SAE Net. And it also wouldn't be anymore powerful either, just a different number representing the same real VALUE.

I apologise if I sound a little arrogant before, but it was from a while back and had completly forgotton all about it until you posted.

Trublu01 · Nov 30, 2005

300bhp/ton said:
Mustangs, Cobra or otherwise still follow the same laws of physics as everything else does.

Very few engines are really underatted, it's just most people don't have a clue about how different meausres are derived. Sad but true.

I even have my suspisions about some of the Fbody claims (and I own one of them!!!!).

Did you know that you can dyno the SAME car on a Dynojet and then on a Mustang Dyno and see upto 20rwhp difference in the results, straight off.

This is because the Mustang Dyno is load bearing and the Dynojet isn't. It does NOT however mean that the car was producing more power on the Dynojet, just that it was derived differently.

And remember most dyno's rate in STD not SAE. So in most cases (without worrying about how it does it) just knock 10rwhp off.

So if a car made 380rwhp STD on a Dynojet. It would be nearer to 350-355rwhp SAE on a Mustang Dyno rated in SAE. This hasn't even taken into account any of the local and atmospheric conditons which should also be corrected for by calculations.

See how easy numbers get mixed up. If a Cobra really is making 350rwhp once every thing is accounted for, then ~390bhp SAE Net at the engine is probably spot on.

Of course you could re-rate the manufactures claimed figure to STD which would probably put it at over 400bhp, but it wouldn't any longer be SAE Net. And it also wouldn't be anymore powerful either, just a different number representing the same real VALUE.

I apologise if I sound a little arrogant before, but it was from a while back and had completly forgotton all about it until you posted.

Umm, are you under age? I don't know about England, but the Mustang Dyno and Dynojet Dyno numbers thing is very, very, very old news. And on a Dynojet 03/04 Cobra's have seen over 380RWHP SAE. Therefore the 03/04 Cobra was/is an underrated car when speaking of HP!

300bhp/ton · Dec 1, 2005

Trublu01 said:
Umm, are you under age? I don't know about England, but the Mustang Dyno and Dynojet Dyno numbers thing is very, very, very old news. And on a Dynojet 03/04 Cobra's have seen over 380RWHP SAE. Therefore the 03/04 Cobra was/is an underrated car when speaking of HP!

That's my point EXACTLY.

If comparing to manufacters numbers to rolling road dyno numbers. A Dynojet gives a HIGHER figure which distorts the figures for comparatives sake.

Lets assume that the 380rwhp you mention on a Dynojet has been accuratley corrected to SAE (also as you mention) and with all other correction factors considered.

HOWEVER - A Dynojet is not a load bearing dyno. So to give a more 'real world' number we need to make an adjustment to account for a load bearing dyno. It is likely to be minus about 20 - 30rwhp. If there are then any high dyno numbers it is most likely to how the operatir has the machine setup. As graph smoothing and correcting can easily show 10-15rwhp to high a number.

Regardless, all the results I have seen, if you add REALISTIC correction factors and drivetrain losses you will generally end up with estimated engine outputs of 389-405bhp type of range. Which would sound about bang on to account for manufacturing tolorancies.

I DO NOT doubt for a second that some 03/4 Cobra's produce more BHP than rated. But that is because it would be good practice for Ford to quote the minimal you should expect and not the maximum. Espcially in light of what happened with Cobra's past. However the claims of 440-450bhp STOCK I feel are optomistic at best.

That aside, the Cobra looks fantastic and sure is one darn fast car that responds really well to mods.

Oh and BTW - this all applies to the Fbody as well. It is reasonaly accepted that the LS1 is underatted, which has been verified by independant test putting a crate LS1 onto an engine dyno.

However there are NO stock LS1's that dyno 320-330rwhp. Sure there are people with graphs that show this, but that doesn't prove anything as without ALL the correction calculations being applied and being tested on a load bearing dyno to SAE standards the numbers will not be comparable to manufacture claims.

To show how easy it can be. Stock crate LS1 (direct replacement for an Fbody) is rated by GM @ 320bhp SAE Net. Although 98-00 cars should only have 305bhp SAE Net. So here's one descrepancy.

Chuck that STOCK crate engine onto an engine dyno. With an electric water pump, no anciallry devices and a set of long tube headers. It produced 429bhp STD.

Has it really gained 110bhp just by adding headers and removing the alternator and power steering pump?

No - what you would need to do is adjust for SAE standards. So having all the anciallary devices attached, plus normal headers and what ever else the standard requires. All this plus the additional correction which is probably needed to counter the different types of dyno used (engine dyno's also vary like chassis dyno's do). And you'd find that the number would probably drop by about 80bhp or so. Giving a total much nearer to 340-350bhp SAE Net, which is right where would be expected as that is what a C5 Corvette has SAE Net.

Following along this line of thought it also highlights how FEW of the 60's and early 70's muscle cars where actually producing those headline numbers. As they where all rated as a gross figure. Which as we can see made a REAL world difference of about 70-80bhp on a LS1.

So a 1960's car claiming 350bhp Gross is probably producing nearer 270bhp if it was rated today using the current system.

It all highlights just how inaccurate DYNO and ENGINE bhp numbers can be, and also how mis-leading they are.

If someone can show me (this I would really lkike to see) an un-biased test of a STOCK 03/4 Cobra engine on an ENGINE dyno being tested to FULL SAE Net standards producing 440-450bhp SAE Net then I will happily believe it and eat humble pie. But until then...

Klay · Dec 12, 2005

I totally agree with you 300bhp, I constantly see people saying how the cobra is underrated yet they all go by the 15% loss rule. I think you have done a good job showing why that rule is really bogus since not all drivetrains have the same efficiency and of course the higher your hp the more you lose with that rule.

It's not like 390 hp is something to scoff at, no need to blow the number even more.

eaton, according to car and driver.

New Member

New Member

New Member

New Member

Banned

Mustang Master

Straight Outta Locash

SPRAYMAN

Straight Outta Locash

SPRAYMAN

Straight Outta Locash

SPRAYMAN

New Member

Straight Outta Locash

New Member

New Member

SPRAYMAN

New Member

New Member

Similar threads

Privacy & Transparency

Privacy & Transparency