whipple 4.0
- Thread starter kumar
- Start date
Fubar
Totally ****** Up
Fuel pressure... the computer is using the injectors to compensate for the drop in fuel pressure. It maintains a consistent A/F. The pressure drops from 48lbs to 42lbs around 6000 rpms.
Yukonranger
GT Owner
If you were losing 130hp in the transaxle, it would melt. 130hp is 330,000 BTU. And that supercharger belt would burn up from slippage if it was transmitting 300hp.
Fubar
Totally ****** Up
Fubar
Totally ****** Up
300hp on the Whipple might be a little high but it would explain the fuel usage.
Wikipedia says the a roots type supercharge is only 50-58% efficient (or inefficient as it appears) at 15lbs of boost. I think the whipple is a little more efficient than this article indicates.
I couldn't find a clear reference on the transaxle efficiency.
Wikipedia says the a roots type supercharge is only 50-58% efficient (or inefficient as it appears) at 15lbs of boost. I think the whipple is a little more efficient than this article indicates.
I couldn't find a clear reference on the transaxle efficiency.
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Yukonranger
GT Owner
1200hp would conservatively require about 600lbs/hr of fuel (100gph). This would equate to .50lb/hp/hr which is pretty aggressive for a supercharged engine. What is you fuel usage?
No. The computer is no longer in closed-loop mode (this is the mode where the ECU is pulsing the injectors and "validating" A/F looking at the O2's and then adjusting the pulse duration accordingly). With mid-to-heavy throttle, the ECU wants to run the car richer than 14.7:1 and the O2's are ONLY good at reporting either over or under 14.7:1 (sometimes referred to as walking the fence). As such, the ECU switches out of closed-loop mode in favor of open-loop mode and the ECU does not look at the O2's at all and the ECU has NO CLUE what the A/F is. In this open-loop mode, the fate of your engine is in the hands of the tuner that created the fuel and ignition tables - and it will blindly follow them.
Empty Pockets
ex-GT Owner
That seems a wee bit high(!) to me too, as the screw compressor has very tight tolerances between the rotors AND, if I remember correctly, the rotors never touch. That fact alone ought to eliminate any REAL big parasitic/friction hp loss shouldn't it???
Maybe there'd be a 300hp loss in a roots type using teflon rotor-to-case seals (or whatever), but even there 300 hp seems like a whole lot to me.
That said, I don't have a degree from M.I.T.! So, what th' heck do I know!:biggrin
OCPETE
GT Owner
Fubar
Totally ****** Up
Holy crap guys... it like you think I'm making this stuff up. I promise this is everything I know about my current situation. I was as shocked as you when I heard the numbers but it is inline with what is happening on the 3.4L.
As for the ECU... Yes, that is what is happening. You are right about the computer not looking at A/F. It sees the drop in fuel pressure and uses a preset table to compensate. I was pretty impressed the the little Ford ECU would have that type of fail safe built in, but it does.
All I know is that the 427Aggies 3.4L Whipple has the fuel pumps running at 90% capacity. My 4.0L Whipple has the fuel pumps working at 100% at 6000rpm. There is a slight drop in fuel pressure at that rpm and the ECU compensate for the drop by using another table to boost fuel injector duty cycle.
I am no expert at all. I am only relaying what I am being told. I would love to hear a different/better explanation. Preferable one that I can fix with a beer in one hand and wratchet in the other.
As for the ECU... Yes, that is what is happening. You are right about the computer not looking at A/F. It sees the drop in fuel pressure and uses a preset table to compensate. I was pretty impressed the the little Ford ECU would have that type of fail safe built in, but it does.
All I know is that the 427Aggies 3.4L Whipple has the fuel pumps running at 90% capacity. My 4.0L Whipple has the fuel pumps working at 100% at 6000rpm. There is a slight drop in fuel pressure at that rpm and the ECU compensate for the drop by using another table to boost fuel injector duty cycle.
I am no expert at all. I am only relaying what I am being told. I would love to hear a different/better explanation. Preferable one that I can fix with a beer in one hand and wratchet in the other.
- Aug 25, 2006
- 4,436
Relax Fubar
You presented your story very well
As you know I have been in contact with Shawn during this process and take all of the numbers out of this situation which seem to be the basis of the differences and it becomes simply is there enough fuel or not.
Initially a problem was considered however I know another 4.0 with similar if not the same issue.
Again you did good thank you
Takes care
Shadowman
- Aug 25, 2006
- 4,436
You are correct as such "boosta pumps" were discussed; no I am not encouraging this but rather sharing the conversation.
Shadowman
Mullet
FORD GT OWNER
I agree 10,000% Thanks soooo much Fubar for continuing to write and share your experiences... it is helpful for everyone, certainly myself included!!!
I just didn't want anyone to have the impression that the ECU was knowledgeable about A/F's when under power. What you say about the ECU monitoring fuel pressure and having the "sense" to make appropriate corrections when/if it falls off is indeed pretty trick!
Again, thanks for sharing... keep it coming!!
Fubar
Totally ****** Up
Thanks Shadowman, it just seems like a lot of folks take great pleasure in telling me why I am wrong. I hate to be an e-dick and about it but it gets a little old. I am just trying to present information to the board in hopes of finding a solution and possibly helping other members should they find themselves in a similar situation. Do you think those numbers are out of line? I know that you do not like to comment until all of the information is in and the research has been done. So when you feel it is appropriate, let me know what you think.
Nota4re, do you see what I'm talking about with the ECU? I did not mean to imply that it is chasing the A/F in open-loop. Rather, that the ECU can, and does, correct for low fuel pressure with another table by adding to the duty cycle of the fuel injector. It just happens to do it so well that there is never a spike in the A/F.
Yukonranger, I do not know what the fuel consumption is, per say. All I know is that my fuel pumps are maxed out and that the 3.4L whipple uses up to 90% of the cars fuel pump capacity. Therefor, it is logical to assume that my fuel pumps are working as intended. It was also suggested by my tuner (Shawn Fischer) that the larger supercharger would probably take more hp to turn. Which makes sense, it has bigger with heavier parts that push more air.
I think we'd all be surprised to see exactly how much hp those things eat up... even in stock form.
I would love to hear the Whipple guys chime in.
Regards,
MM
When we were tuning cars in the past, we did not like to push the injectors past about 85% (90% max) duty cycle, same with the fuel pumps. Anything more and you have no margin for error. While some may consider boost-a-pumps a band-aid fix, they do work and are certainly less expensive and easier to test than upgrading the stock fuel pump. Injectors for GTs are readily available too, so you should be able to tell if this cures the issue you are having while running at 'the limit'.
Does anyone have any REAL data on the 4.0L whipple...meaning increase over stock using the same dyno??? Without a before dyno, the numbers really don't mean much. We had 3 Dynojet dynos within 5 miles of a shop. On the same day with roughly the same temps (+/- 5 degrees) we had readings that ranged in power by 30rwhp. As a result, I use a dyno just to see increases with mods, tuning etc..
Does anyone have any REAL data on the 4.0L whipple...meaning increase over stock using the same dyno??? Without a before dyno, the numbers really don't mean much. We had 3 Dynojet dynos within 5 miles of a shop. On the same day with roughly the same temps (+/- 5 degrees) we had readings that ranged in power by 30rwhp. As a result, I use a dyno just to see increases with mods, tuning etc..
Moderators Note.
Gentlemen,
Threads such as this one are most informative and quite useful. I believe it would benefit everyone concerned however, if theory and speculation were presented as such and those items known to be factual as result of actual testing are also presented as such.
The pioneers take the arrows and Mark is blazing a trail here. I am not an automotive engineer but it is common knowledge that an automobile supercharger can use up to one third of an engines power to drive that mechanism and they do not burn up as result of belt slippage. The Ford GT500 Mustang produces an honest 500 hp but on a Dyno they are only able to manage around 400 rearwheel horsepower. That's a 100 hp loss in the drivetrain of a 500 hp car and neither the transmission nor the rear end melts.
Even a very efficient gasoline engine will only be able to extract 20% or less of the total energy contained in a gallon of fuel and will send the remaining 80% into the atmosphere as either heat, emissions, or unburned fuel. Every surface of an automobile's drivetrain from the air cleaner to the surface of the tires, not just the radiator, is constantly bleeding heat into the atmosphere.
I believe a detailed analysis would show that Fubar's power loss figures are not that far off the mark. Yeah, that's a lot of BTUs but that heat does not stay bottled up in the supercharger and transaxle. Like all of the other frictional losses in any automobile, it is quickly bled off into the surrounding air.
"130hp is 330,000 BTU" is a fact and is properly presented as such. "If you were losing 130hp in the transaxle, it would melt".....and....."that supercharger belt would burn up from slippage if it was transmitting 300hp" is speculation and while this theory is a positive contribution to the discussion, it would more properly be presented as theory rather than fact.
I don't wish to ruffle anybody's feathers, I do want to encourage the free exchange of ideas and this is best accomplished when facts backed with historical testing are presented as such and when inferences, theory, and speculation, are also presented as such.
Chip
Gentlemen,
Threads such as this one are most informative and quite useful. I believe it would benefit everyone concerned however, if theory and speculation were presented as such and those items known to be factual as result of actual testing are also presented as such.
The pioneers take the arrows and Mark is blazing a trail here. I am not an automotive engineer but it is common knowledge that an automobile supercharger can use up to one third of an engines power to drive that mechanism and they do not burn up as result of belt slippage. The Ford GT500 Mustang produces an honest 500 hp but on a Dyno they are only able to manage around 400 rearwheel horsepower. That's a 100 hp loss in the drivetrain of a 500 hp car and neither the transmission nor the rear end melts.
Even a very efficient gasoline engine will only be able to extract 20% or less of the total energy contained in a gallon of fuel and will send the remaining 80% into the atmosphere as either heat, emissions, or unburned fuel. Every surface of an automobile's drivetrain from the air cleaner to the surface of the tires, not just the radiator, is constantly bleeding heat into the atmosphere.
I believe a detailed analysis would show that Fubar's power loss figures are not that far off the mark. Yeah, that's a lot of BTUs but that heat does not stay bottled up in the supercharger and transaxle. Like all of the other frictional losses in any automobile, it is quickly bled off into the surrounding air.
"130hp is 330,000 BTU" is a fact and is properly presented as such. "If you were losing 130hp in the transaxle, it would melt".....and....."that supercharger belt would burn up from slippage if it was transmitting 300hp" is speculation and while this theory is a positive contribution to the discussion, it would more properly be presented as theory rather than fact.
I don't wish to ruffle anybody's feathers, I do want to encourage the free exchange of ideas and this is best accomplished when facts backed with historical testing are presented as such and when inferences, theory, and speculation, are also presented as such.
Chip
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Fubar
Totally ****** Up
My big concern with a boost-a-pump is the device failing and I have no idea that it failed. I really don't like having two fuel pumps either. One can fail and you wouldn't notice because it would drive around (light load) fine. However it would go lean when you pushed it. I guess it is just a problem I'll have to live with.