Handling/drive-ability for optimistic engine options.
Discussion
I've been working on T/C and a switched low/high power map, the low/high power map is all but done but I have to figure a reliable way to bleed boost for low power option.
T/C is interesting to say the least.
It appears to be a real can of worms and I think I will need a skid pan and a professional live mapper in car to get this done in any way that is going to be useful.
T/C is interesting to say the least.
It appears to be a real can of worms and I think I will need a skid pan and a professional live mapper in car to get this done in any way that is going to be useful.
All modern EMSs are "Torque based". That is they use engine torque as there primary arbitor. As such the accelerator pedal is simply used as a driver demand, and it's position is used to set a target torque at that moment in time. Then the EMS will work out, using a mixture of model based maths and look up characteristic tables, how it should operate it's actuators (throttle, injectors, ignition, cam position etc etc) so that the engine makes the target torque at the flywheel. Due to this, despite changing parameters, such as engine temp, air temp, fuel grade etc the flywheel torque will always be that which the driver is demanding (unless other systems demand a different torque (traction control, gearbox etc).
The exact mapping of the driver demand to engine speed and road speed is a fine art, and there are a few different ways of doing it to make for different driveability characteristics.
On the engine side, once you have electronic control of the airpath (ie, the driver isn't opening the throttle directly, so you can control the engines air charge (and hence it's min/max torque for any given engine speed) independently. This has massive benefits on a forced induction engine, where you can deliberately retard ignition timing (reduces torque) but increase throttle opening, resulting in a large torque "back up" value. This allows the EMS to react very quickly and to linearise the flywheel torque output, despite things such as suddenly changing boost pressure etc.
Most modern turbo engines are moving to fully electronic wastegate actuators to effectively give a full and un-impeaded range of turbo speed (and hence boost pressure) control.
For example, BMW M3/M4: (the black box on the rhs)
By being able to control wastegate bypass flow completely independently of manifold pressure, you can play lots of tricks on the throttle response etc
The exact mapping of the driver demand to engine speed and road speed is a fine art, and there are a few different ways of doing it to make for different driveability characteristics.
On the engine side, once you have electronic control of the airpath (ie, the driver isn't opening the throttle directly, so you can control the engines air charge (and hence it's min/max torque for any given engine speed) independently. This has massive benefits on a forced induction engine, where you can deliberately retard ignition timing (reduces torque) but increase throttle opening, resulting in a large torque "back up" value. This allows the EMS to react very quickly and to linearise the flywheel torque output, despite things such as suddenly changing boost pressure etc.
Most modern turbo engines are moving to fully electronic wastegate actuators to effectively give a full and un-impeaded range of turbo speed (and hence boost pressure) control.
For example, BMW M3/M4: (the black box on the rhs)
By being able to control wastegate bypass flow completely independently of manifold pressure, you can play lots of tricks on the throttle response etc
Magic919 said:
You'd leave the pedal gear alone and just map the response in the ECU these days. Valet mode would swap maps when you flick the switch.
Oh, well that's interesting. I had read enough to know generally a TAC with lookup tables sets output trottle body position based on pedal sensors, and knew some manufacturers use multiple maps/tables for various conditions (didn't know if GM did or not)... but I didn't know that could be user selectable.That would be pretty cool. Any chance you know how many maps you can create, and how easy it is to swap maps from the user perspective in cockpit? A true valet mode with minimal power (like 10%) would be very useful. Something that keeps power sane, like under 500hp, for normal driving might be useful. I also wonder how the interaction of throttle and boost with a supercharger might work... if you had a map that kept the bypass open (say on a whipple), but had useable power, couple of hundred horses maybe, for everyday driving, it might provide a way to run pump gas daily and race gas for more enthusiastic sprints without swapping pulleys?
Max_Torque said:
All modern EMSs are "Torque based". That is they use engine torque as there primary arbitor. As such the accelerator pedal is simply used as a driver demand, and it's position is used to set a target torque at that moment in time.
OK, well that is interesting too. How does the EMS monitor engine torque? Is that a lookup table too of sorts, a "should be" value for combination of RPM, throttle, timing, fuel, etc.? Or does it monitor engine load more directly? Makes me think my original PD vs centrifugal charger question becomes relegated to the back seat, with throttle mapping really being the pertinent issue. I mean, if the EMS sets conditions to achieve a torque target for a given pedal position, does it really matter if that torque is generated vs PD or centri? And if your mapping requests say linear torque for linear pedal travel, can the EMS make that happen (within bounds of what the engine can output of course) for either type of charger?If so, the a PD/whipple may have more low end torque, but wouldn't "force" you to use it depending on how you had your pedal mapped. Well, of course the right foot is always the ultimate torque control, but what I mean is it wouldn't necessarily be more twitchy or prone to melting tires from the line or out of a corner than a centri unless that is how throttle was mapped. Might be nice to have that low torque, for overtakes in 5th for example, knowing it wouldn't make it any harder to put down the power.
Interesting... I'm glad the discussion wandered in this direction. More to read about!
With an Ultima you are not buying a car you will use every day. A trip out in it will be a 'special occasion' and you adjust your driving accordingly.
Most owners will not use the car in the wet and certainly not when it is icy. Cleaning after use to keep her looking good will take longer than the drive!
Throttle travel is long and very progressive with the DBW LS setup. To get things really out of shape with warm, sticky tyres you do need to be driving at very silly speeds on public roads. Major throttle openings in first gear will spin up the wheels and at higher revs in second too. But the Ultima is like most race cars in that you feed in the power on exiting a corner finally nailing it once straight.
I fail to see why you would want traction control on track (where you can be a bit of a hooligan) and for the reasons above I fail to see why you want the complication and 'nannying' on the road.
The fun in driving an Ultima is the raw experience where your right foot is your traction control.
This may be an age thing. I grew up with cars that had not got TC, ABS, PS, ASC or any other abbreviation you can think of. If you came to an Ultima having been used to TC then I can understand the fear of being unable to 'catch' the rear when it steps out.
I would spend the money on some track time and instructor fees. Better value and more fun.
Paul
Most owners will not use the car in the wet and certainly not when it is icy. Cleaning after use to keep her looking good will take longer than the drive!
Throttle travel is long and very progressive with the DBW LS setup. To get things really out of shape with warm, sticky tyres you do need to be driving at very silly speeds on public roads. Major throttle openings in first gear will spin up the wheels and at higher revs in second too. But the Ultima is like most race cars in that you feed in the power on exiting a corner finally nailing it once straight.
I fail to see why you would want traction control on track (where you can be a bit of a hooligan) and for the reasons above I fail to see why you want the complication and 'nannying' on the road.
The fun in driving an Ultima is the raw experience where your right foot is your traction control.
This may be an age thing. I grew up with cars that had not got TC, ABS, PS, ASC or any other abbreviation you can think of. If you came to an Ultima having been used to TC then I can understand the fear of being unable to 'catch' the rear when it steps out.
I would spend the money on some track time and instructor fees. Better value and more fun.
Paul
F.C. said:
I've been working on T/C and a switched low/high power map, the low/high power map is all but done but I have to figure a reliable way to bleed boost for low power option.
T/C is interesting to say the least.
It appears to be a real can of worms and I think I will need a skid pan and a professional live mapper in car to get this done in any way that is going to be useful.
A waste gate seems the best solution. Used a lot in race cars that are superchargered to give the desired torque the drive wants and chassis can handle. Alternatively restrictor ages are also used, but you can't change the boost on demand like you can with the waste gate. T/C is interesting to say the least.
It appears to be a real can of worms and I think I will need a skid pan and a professional live mapper in car to get this done in any way that is going to be useful.
Storer said:
I fail to see why you would want traction control on track (where you can be a bit of a hooligan) and for the reasons above I fail to see why you want the complication and 'nannying' on the road.
The fun in driving an Ultima is the raw experience where your right foot is your traction control.
This may be an age thing. I grew up with cars that had not got TC, ABS, PS, ASC or any other abbreviation you can think of. If you came to an Ultima having been used to TC then I can understand the fear of being unable to 'catch' the rear when it steps out.
I would spend the money on some track time and instructor fees. Better value and more fun.
+1000The fun in driving an Ultima is the raw experience where your right foot is your traction control.
This may be an age thing. I grew up with cars that had not got TC, ABS, PS, ASC or any other abbreviation you can think of. If you came to an Ultima having been used to TC then I can understand the fear of being unable to 'catch' the rear when it steps out.
I would spend the money on some track time and instructor fees. Better value and more fun.
By all means, everyone who's paid the entry fee should feel free to build the car to suit himself. That said, there are likely better choices available for those who desire all the "modern" electronic crutches. No need to force this square peg into a round hole for which it was never intended. For those with the inclination, skill, and proficiency (or desire to attain and maintain same) to enjoy the sensations of an unrestrained, high HP, RWD beast in the classic mode, the Ultima is unparalleled.
Ken
F.C. said:
I have to figure a reliable way to bleed boost for low power option.
If you have a positive displacement supercharger, ie one that does not use internal compression, then "Bleeding boost" is simply a bypass throttle valve around the charger! Ideally you make this an electronically controlled valve to give you whatever boost pressure you want vs accelerator pedal position. Something like the Hella electric wastegate control valve from a diesel turbo would be easy to drive and to actuate a small bypass valve (50mm dia would probably do it). Some supercharged cars use a vacuum operated valve to do this, but this valve is necessarily limited in it's capability (requiring plenum to be at a vacuum to be opened and often "slamming shut" somewhat aggressively on tip-ins (unlike an electric actuator that can be gradually shut at any speed)
Storer said:
I would spend the money on some track time and instructor fees. Better value and more fun.
That's going to be the first thing on my to do list once car is finished. Have to start first though![quote]Throttle travel is long and very progressive with the DBW LS setup. To get things really out of shape with warm, sticky tyres you do need to be driving at very silly speeds on public roads. Major throttle openings in first gear will spin up the wheels and at higher revs in second too. But the Ultima is like most race cars in that you feed in the power on exiting a corner finally nailing it once straight.
I fail to see why you would want traction control on track (where you can be a bit of a hooligan) and for the reasons above I fail to see why you want the complication and 'nannying' on the road.
chuntington101 said:
A waste gate seems the best solution. Used a lot in race cars that are superchargered to give the desired torque the drive wants and chassis can handle.
From my understanding, although sometimes done by street guys, venting/bypassing while under boost creates excess heat and drag and is generally discouraged by Whipple. Right?Max_Torque said:
If you have a positive displacement supercharger, ie one that does not use internal compression...
Yeah, so that rules out the Whipple I suppose. From what I can gather, aside from cost, this may be one of the biggest disadvantages of a Whipple - the difficulty in controlling boost levels short of pulley swaps.BTW, and OT...
How does the PM system on PH work??? I've received a couple of email from forum members sending me a PM regarding this thread (thanks, great info!), to which I responded via email.
Don't know if the email response was sent or received, so thought I'd send a response PM through PH just in case. I can't find the damned thing anywhere! And I realized I can't even figure out how to send a new PM to someone should I want or need to.
Looked at the website feedback portion and didn't see a how to for idiots like me. Help!?
How does the PM system on PH work??? I've received a couple of email from forum members sending me a PM regarding this thread (thanks, great info!), to which I responded via email.
Don't know if the email response was sent or received, so thought I'd send a response PM through PH just in case. I can't find the damned thing anywhere! And I realized I can't even figure out how to send a new PM to someone should I want or need to.
Looked at the website feedback portion and didn't see a how to for idiots like me. Help!?
rhosch said:
...but would be interested in a true valet mode that cuts power to some minimal level for, well... actual valet use isn't out of the question!
Really?!? OK…but I'd think twice (at least) about that. Even if you could keep them under, say, 15 MPH, I wouldn't trust them not to ding the car. I never valet my cars, ever. If I know that I'm going to a place with valet service, I contact them ahead of time and arrange to self-park, preferably right out in front.So long as I own it, the only other people who'll ever drive my GTR are the two friends who regularly assisted me during the build (both experienced race drivers) and, maybe, my wife (carefully around the neighborhood only).
Ken
Corsair613 said:
So long as I own it, the only other people who'll ever drive my GTR are the two friends who regularly assisted me during the build (both experienced race drivers) and, maybe, my wife (carefully around the neighborhood only).
OK, you caught me. Probably have the wife, brother, cousin, etc. and especially (GASP!!) children in mind more than anything else. Not sure if I would ever let any of them drive the car, but I wouldn't summarily rule it out either and a low power option might come in handy if not overly complex to implement.rhosch said:
....How does the PM system on PH work???......
To send a PM click on the person you wish to contact which will take you to their profile. In the top right corner of the profile page click on 'Email me'.It will send a mail but you don't see the email address. You will only start to see the address after you have entered into a back and forth via mail.
Steve
rhosch said:
chuntington101 said:
A waste gate seems the best solution. Used a lot in race cars that are superchargered to give the desired torque the drive wants and chassis can handle.
From my understanding, although sometimes done by street guys, venting/bypassing while under boost creates excess heat and drag and is generally discouraged by Whipple. Right?
I wouldn't worry about the heat. When in low boost mod you will probably be pushing the charge cooling system LESS than you would be on full attack mode anyway.
Storer said:
With an Ultima you are not buying a car you will use every day. A trip out in it will be a 'special occasion' and you adjust your driving accordingly.
Most owners will not use the car in the wet and certainly not when it is icy. Cleaning after use to keep her looking good will take longer than the drive!
Throttle travel is long and very progressive with the DBW LS setup. To get things really out of shape with warm, sticky tyres you do need to be driving at very silly speeds on public roads. Major throttle openings in first gear will spin up the wheels and at higher revs in second too. But the Ultima is like most race cars in that you feed in the power on exiting a corner finally nailing it once straight.
I fail to see why you would want traction control on track (where you can be a bit of a hooligan) and for the reasons above I fail to see why you want the complication and 'nannying' on the road.
The fun in driving an Ultima is the raw experience where your right foot is your traction control.
This may be an age thing. I grew up with cars that had not got TC, ABS, PS, ASC or any other abbreviation you can think of. If you came to an Ultima having been used to TC then I can understand the fear of being unable to 'catch' the rear when it steps out.
I would spend the money on some track time and instructor fees. Better value and more fun.
Paul
I wonder how "Monkey" would drive an Ultima on track. That would be a sight to see Most owners will not use the car in the wet and certainly not when it is icy. Cleaning after use to keep her looking good will take longer than the drive!
Throttle travel is long and very progressive with the DBW LS setup. To get things really out of shape with warm, sticky tyres you do need to be driving at very silly speeds on public roads. Major throttle openings in first gear will spin up the wheels and at higher revs in second too. But the Ultima is like most race cars in that you feed in the power on exiting a corner finally nailing it once straight.
I fail to see why you would want traction control on track (where you can be a bit of a hooligan) and for the reasons above I fail to see why you want the complication and 'nannying' on the road.
The fun in driving an Ultima is the raw experience where your right foot is your traction control.
This may be an age thing. I grew up with cars that had not got TC, ABS, PS, ASC or any other abbreviation you can think of. If you came to an Ultima having been used to TC then I can understand the fear of being unable to 'catch' the rear when it steps out.
I would spend the money on some track time and instructor fees. Better value and more fun.
Paul
Max_Torque said:
With an electronic throttle and good mapping you can make any amount of power "driveable" imo. Even high boost turbo power these days is fairly easily mapped into a reasonably linear delivery using a few tricks!
exactly this.... I used to have a 500bhp Ultima and now have a noble, so have done the big HP NA and bigger HP turbo.
I run my noble at full boost (over 700bhp) all the time... as its forced induction I can vary the boost and thus power depending upon throttle position so its easier to drive hard and fast on the throttle than an equivalent NA engine (without traction control) and I have tweaked the boost to make a massive power band so that peak power is held for 1500rpm and holds to the 8000rpm redline with 400ftlb available from 4000rpm.... all that from a 3.0L V6. Imagine what a decent similar spec LS would do!
My car is an absolute pussycat to drive rain or shine on the road... even easier than my 500bhp NA SBC Ultima which I thought was easy to use as well.
Modern turbos a proper design of exhaust and external waste gates mean they can have the throttle response to rival good NA engines with no lag.
Steve_D said:
To send a PM click on the person you wish to contact which will take you to their profile. In the top right corner of the profile page click on 'Email me'.
It will send a mail but you don't see the email address. You will only start to see the address after you have entered into a back and forth via mail.
Steve
Thanks, finally! Would have never found that.It will send a mail but you don't see the email address. You will only start to see the address after you have entered into a back and forth via mail.
Steve
Whipple now an option for Ultima Evo LS7 according to factory update on Facebook.
1000+hp and you know it will fit/work.
All I'll say on the subject beyond that (as I know how alluring the prospect of mega power is - even if the reality is a bit different), if I were to build another, it would be a NA LS7. But that may be because I'm getting old and lazy
Even with 300bhp the car will be more far more capable than most drivers.
Good luck with the build!
1000+hp and you know it will fit/work.
All I'll say on the subject beyond that (as I know how alluring the prospect of mega power is - even if the reality is a bit different), if I were to build another, it would be a NA LS7. But that may be because I'm getting old and lazy
Even with 300bhp the car will be more far more capable than most drivers.
Good luck with the build!
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