A&Q about Lotus
Q:
Originally Posted by Val
Apex, thats a great insight! really appreciate your help
So, basically would you rather go for a supercharger with a nicely remapped ecu, or a turbo with piggy back which might have some minor issues (eg rough idling)?
No, I'd rather go with a turbo with a nicely remapped ECU.
As for people getting the emanage to work, I have heard of exactly 1 person who claims they have it sorted out and its great, and many, many who haven't. I myself have tried and been unsatisfied with the results. Another tuner who I respect a lot (we both work in Grand AM and ALMS) spent some time struggling with the same issues. If you have it running on Emanage, please tell us the secret.
A:
Val,
According to the link to komo-tec, they are using a centrifugal supercharger not a Lysholm. Something more to think about...
A:
Originally Posted by milcher
Val,
According to the link to komo-tec, they are using a centrifugal supercharger not a Lysholm. Something more to think about...
Opps, youre correct!
What is centifugal anyway? Never heard about it...
A:
A centrifugal supercharger looks like a belt driven turbo. Since they are become more efficient at higher rpms, they are usually used on big displacement motors that make large amounts of naturally aspirated low end power. Not an ideal solution for a small displacement motor that is hurting in the low end power department like the 2ZZ.
A:
Originally Posted by milcher
A centrifugal supercharger looks like a belt driven turbo. Since they are become more efficient at higher rpms, they are usually used on big displacement motors that make large amounts of naturally aspirated low end power. Not an ideal solution for a small displacement motor that is hurting in the low end power department like the 2ZZ.
Hmm, but he torque curve seems to be very nice
A:
Compare the komo-tec torque curve to these dyno plots, it shows to the Eaton Tri-Point set up and the FF275:
A:
I'd go Supercharger simply becasue of the unpredictability of a turbo's rubber-band acceleration - specifically around corners when you modulate the throttle a bit.
I say this without having driven a turbo Elise, but I've driven plenty of turbo charged cars and this is *always* the case... At least when compared to an NA version of the same car.
The few supercharged cars I've driven have not had this issue - always very predictable/linear torque - as can be seen on the dyno above.
ymmv.
A:
Originally Posted by BrianK
I've driven plenty of turbo charged cars and this is *always* the case... At least when compared to an NA version of the same car.
No. It's only the case when the turbo is not properly sized, or the goal is maximum HP without regard to low-end power.
Not to mention our current car ain't exactly smooth on a curve when you're at the point of cam changeover.
Val, what kind of gas do they use in Germany? Same as Russian gas? If they're the same, that might be an advantage.
A:
Originally Posted by milcher
Compare the komo-tec torque curve to these dyno plots, it shows to the Eaton Tri-Point set up and the FF275:
Am i missing something here? To me it looks like centrifugal is pretty much identical to eaton
forcedfed looks prettu messy on the other hand?
A:
Originally Posted by Taxcheat
No. It's only the case when the turbo is not properly sized, or the goal is maximum HP without regard to low-end power.
Then what is an example of a car with a properly sized Turbo and does one exist for the Elise?
Not to mention our current car ain't exactly smooth on a curve when you're at the point of cam changeover.
all the more reason to not make the situation worse.
A:
Originally Posted by Val
Am i missing something here? To me it looks like centrifugal is pretty much identical to eaton
forcedfed looks prettu messy on the other hand?
I agree about the Forcedfed. I'd like to see some other graphs of the Forcedfed for comparison. I remember seeing a graph from an install in Colorado, an earlier one. The A/F ratio was pretty lean and things weren't too steady if I recall.
As far as the Eaton graph, yes, It looks like a straight line. It's almost too good to be true. Hope it is. I'd like to see other Eaton graphs for comparison.
Val,
the only centrifugal that would fit in our cars is the Rotrex as far as I know. Ask them what it is, a C30-74, C30-84 or unlikely smaller or bigger one.
A:
Originally Posted by BrianK
Then what is an example of a car with a properly sized Turbo and does one exist for the Elise?
T03/04 on an Impreza 2.5RS. Don't remember the A/R. After the full boost surge (2500-3000 RPM), power delivery was perfectly smooth. Is there a properly sized Elise turbo? Again, the problem you probably are seeing is boost junkies that are going for max horsepower not driveability. Boost is like crack.
I rode in a PF Supercars one-off Elise turbo. The driver/owner notices the cam change, but it seemed seamless to me -- I didn't notice it at all.
I don't see where you'd ever be off boost on a tracked turbo Elise. Especially with a ball bearing turbo, lag isn't an issue. With conservative turbo sizing, boost & tuning, peaky delivery isn't an issue either.
A:
Originally Posted by Val
Am i missing something here? To me it looks like centrifugal is pretty much identical to eaton
forcedfed looks prettu messy on the other hand?
A few things, first of all I threw up the dynos just for comparison and that's it. The FF275 dyno run is fzust's car, I read from a post on MM that his car had an air leak or something that maybe caused the bumpy graph. Maybe he'll chime in with more insight since he knows much, much more than me about building turbos and superchargers.
Disregarding the #'s, take a look at the Eaton torque curve and notice how flat it is. It is more flat than the centrifugal plot. If you're interested in doing the research, I'd recommend looking at a similar engine that is more frequently supercharged, where there would be more data available. Honda S2000's come to mind as a possible candidate for Eaton vs. turbo vs. centrifugal data.
A:
Originally Posted by Taxcheat
T03/04 on an Impreza 2.5RS. Don't remember the A/R. After the full boost surge (2500-3000 RPM), power delivery was perfectly smooth. Is there a properly sized Elise turbo? Again, the problem you probably are seeing is boost junkies that are going for max horsepower not driveability. Boost is like crack.
I rode in a PF Supercars one-off Elise turbo. The driver/owner notices the cam change, but it seemed seamless to me -- I didn't notice it at all.
I don't see where you'd ever be off boost on a tracked turbo Elise. Especially with a ball bearing turbo, lag isn't an issue. With conservative turbo sizing, boost & tuning, peaky delivery isn't an issue either.
Isnt' the t03/04 a big ol' thing?
While I hope you're right, I'm going to file this in the "I'll believe it when I see it" folder (no disrespect). Fact is when you take your foot off the gas pedal, pressure goes away; when you put it back on, it has to come back & it takes more time to do that then it does for me to push my pedal to the floor - thereby making for rubber-band-like acceleration. The turbo (and exhuast gas) has to keep up with my foot & that's a tall order - all the while, my foot is trying to keep the car in line, so the power delivery is two steps behind - it must first wait for my brain, then the turbo.
... and so the question remains, is there a "perfectly" sized turbo for the Elise? I kinda doubt it (again, not having driven one, it's hard for me to say, but I'm also fairly anti-turbo, so take that with a grain of salt). At least the supercharger is attached to a belt that's attached to the engine so there isn't much (if any) of a speed-up when you put your foot back down.
Seems that this is always where FI discussions go, so I'll leave it with that. I don't like turbos. I kinda like superchargers. I'd prefer a bigger engine that weighed less.
A:
Originally Posted by apex speed tech
No, I'd rather go with a turbo with a nicely remapped ECU.
As for people getting the emanage to work, I have heard of exactly 1 person who claims they have it sorted out and its great, and many, many who haven't. I myself have tried and been unsatisfied with the results. Another tuner who I respect a lot (we both work in Grand AM and ALMS) spent some time struggling with the same issues. If you have it running on Emanage, please tell us the secret.
I have the HASS turbo and it's running phenominally well with the eManage ultimate. It's a stable tune and can pass emission testing. My tuner is Giles from Holyroller dyno.
A:
Any other disadvantages to centrifugal s/c apart from the torque cure (which looks pretty good in fact)?
A:
The centrifugal supercharger has some technical advantages to the turbocharger
* typical non turbo car powerband but with much more torque at low and middle revs
* lower thermal load to the piston and exhaust valves
* same cam profiles than a non turbo engine
* lower thermal load to the engine bay peripheric
* standard exhaust system
As advantage of the centrifugal supercharger to the "classic superchargers" like Roots you could see the following points like:
* very high effectiv (up to 80%)
* low noise (not like for example the Lysholm Charger)
* lower charger and intercooler temperature
* much lighter system like a "classic Charger"
* easy boost control
* no big modifications on the standard inlet manifold necessary
* Plug&play fitting
A:
I have the HASS turbo and it's running phenominally well with the eManage ultimate. It's a stable tune and can pass emission testing. My tuner is Giles from Holyroller dyno.
Can you put me in touch with your tuner? I'd like to know what he'd done differently. Do you have a non-learning ECU? Have you been able to disconnect the O2 sensors without triggering a code? Or are you using a split-second type 02 controller with the Emanage? We've theorized that might all work, but its easier and we get better results by just piggybacking a standalone.
The centrifugal supercharger has some technical advantages to the turbocharger
* typical non turbo car powerband but with much more torque at low and middle revs
* lower thermal load to the piston and exhaust valves
* same cam profiles than a non turbo engine
* lower thermal load to the engine bay peripheric
* standard exhaust system
I disagree with many of these. I believe they'd based in comparing high-boost turbocharged cars to low boost supercharged cars. The first three don't hold weight it if you compare engines with similar boost levels. Here's why.
1. Typical non-tubo car powerband but with much more torque at low and middle revs
All other things being equal, torque is a function of boost and CR. That's it. So if you have a supercharged car running the same CR as a turbo car, and running the same boost, the only reason in the world you'd have more torque at low and middle revs in the turbo car is that you have too big a turbo. Once again: All other things being equal, a properly sized ball-bearing turbocharger will outperform a centrifugal supercharger for a given boost level. Spool up is not an issue. By the time the supercharged engine is making revs for effective boost, the turbo is already at max boost. There are many, many examples of these in engines I've built.
* lower thermal load to the piston and exhaust valves
Thermal load is a function of efficiency. Since the turbo speed is not directly tied to crankshaft speed, it (again, if properly sized) can run near max efficiency for a larger part of the rev range. So thermal loading is less, not more.
* same cam profiles than a non turbo engine
What? Where'd you get this? The cam doesn't know its turbocharged or supercharged. Boost is boost. This leads me to believe you're comparing two different boost levels.
* lower thermal load to the engine bay peripheric
* standard exhaust system
Yes, true. But you've saved yourself the drivebelt concerns too, so it may be a wash.
The turbocharger only looks bad compared to the supercharger because people don't normally compare equivolent systems. Typical built Subarus and Evos are running 22psi of boost. Yeah, they're going to have lag and such, but its a compromise for top-end power. Don't use these kinds of cars to benchmark turbos.
And yes, you're right, a Turbo Elise CAN have less low end response and more lag than a supercharged car. But the cars which will exhibit these characteristics are optimized for 300HP. Find me an S/C Elise with 17psi of boost and 300HP. Again, try comparing apples to apples. The turbo car will come out on top.
A:
Originally Posted by BrianK
Fact is when you take your foot off the gas pedal, pressure goes away; when you put it back on, it has to come back & it takes more time to do that then it does for me to push my pedal to the floor - thereby making for rubber-band-like acceleration.
Fortunately, it doesn't work that way. The only way that you would fall off boost on the track is if you're in too high of a gear. Solution: next time use a lower gear. In fact, this is precisely what you do with the stock 2ZZ bogs down.
All I can say is that I've driven the same car on the track N/A and aftermarket turbo'd and a later model with a factory turbo (the same car I just drove about an hour ago). The turbo cars are far easier to drive on the track because you won't fall asleep waiting for torque to pull out of a tight corner.
I think you're confusing nice street turbo kits with big-turbo race cars that have a very narrow, high RPM powerband. Those are the only cars that need left-foot braking to keep on the boost.
A:
Look for the user "SpeedyK" and ask him a bit more about the Bemani supercharger and his own personal experiences; I wouldn't discount it so quickly. He has an Exige Cup with the Bemani SC in Switzerland and it is really quite nice. I had a chance to try it and the power delivery is superb. Just like a big, fat, naturally aspirated engine. It is also a car which absolutely matches its performance numbers in independent tests (compared to, for example, Lotus's own wildly optimistic acceleration figures for the Exige S). As a mech. eng., I was really impressed when I looked around and under the car; the install is very well done.