Next Generation in Supercharging Means 275whp!

[Dave]

Originally Posted by robains

I plan to upgrade the unit with the Data Logging capabilities which will provide some additional learning capabilities.

The data logging is nothing short of fantastic...loads of monitored parameters too with adjustable sampling rates. Starts/stops automatically, so no forgetting. It's an option that I can't imagine doing without now that I have it.

[Murix]

Originally Posted by ZJChaser

after getting devistated by a Viper ACR in the banking at cal speedway last weekend....more that 300whp will be needed to run with one of those up top....the other problem...we run out of gearing long before they do, oh well.

That's not really that bad if that is what you are comparing your top end to is it? Even with brick aerodynamics Viper ACR's pull like freight trains. Lots of power and torque seem to have that effect. Was it stock?

[Bleu Omdurman]

just a few data points.

Cd of a few cars:
Porsche 996 Turbo - 0.31
Ferrari 360CS - 0.33
Viper GTS - 0.35
Ford GT - 0.36
Lotus Exige - 0.47

[robains]

That doesn't seem right to me on the CD numbers. For one the frontal area of the Lotus is considerably smaller. How is it being measured?

170 mph is attainable at 255 wHP (trust me - with EFI and stock 6 speed) - take the rear wing off. But to hit 200 mph, I agree, you'll need considerably more wHP - Viper ACR stock will do about 202 mph on 600 HP. If Lotus CD is indeed that bad, then you'll need more than 600 HP as weight starts to get irrelevant at those speeds.

Personally I think anyone doing 170 mph in a Lotus without a full roll cage is crazy - me included .

Torque doesn't help top speed, HP does. Anyone that has done 180+ on a motorcycle and popped their head up over the front fairing will understand the sheer forces involved -- pretty friggin amazing.

[darkSol]

According to the page 162 of the Jeremy Walton "Lotus Elise: The Official Story Continues" book... the drag coefficient for the Series 2 Elise is actually 0.36... Might be a bit higher for the 111R SportsPack due to the wider front tires and "poking through the diffuser" exhaust... perhaps 0.38... certainly not anything close to 0.47.

Sorry about the bad quality attachment - it's a alt-prtsc from the Amazon online book viewer. It helps if you squint

BTW, I also wish that we had a lightest configured base weight of 710kg (1566 lbs.) instead of 860kg (1896 lbs.)... that's 150kg (330 lbs.). But I guess we needed airbags, A/C and stuff... Arggh!!!

[charliex]

i've got the S as .434

[xtn]

Originally Posted by robains

170 mph is attainable at 255 wHP (trust me - with EFI and stock 6 speed) - take the rear wing off.

That's very interesting.

The math puts the Elise/Exige at 156mph at 8000 rpm in sixth gear. 165 might be had at 8500 rpm, if your EFI will allow that rpm in sixth gear. I'm guessing it will because you must have upped your redline to just over 8750 rpm to touch 170 miles per hour with the stock transmission and stock sized tires.

xtn

[jhnmdahl]

Originally Posted by robains

That doesn't seem right to me on the CD numbers. For one the frontal area of the Lotus is considerably smaller. How is it being measured?

Frontal area has nothing to do with the drag coefficient - you divide drag of the car by the drag on a plate with the same frontal area to calculate Cd, eliminating frontal area from the equation. A small model of the car should have approximately the same drag coefficient as a life-sized or double-sized car with the same proportions.

John

[Chili Red]

Originally Posted by jhnmdahl

Frontal area has nothing to do with the drag coefficient - you divide drag of the car by the drag on a plate with the same frontal area to calculate Cd, eliminating frontal area from the equation. A small model of the car should have approximately the same drag coefficient as a life-sized or double-sized car with the same proportions.

John

How can that be true...

Example: Take a 5"x5" square piece of card board and wave in through the air. You can feel the amount of drag being created. Now do the same thing with a 20"x20" piece of card board and feel the difference.

BTW, I know nothing about calculating Cd, but what you said does not make sence to me.

[luxige]

^^^Your example describes total drag, not cD. Think of cD as a measure of the efficiency of the shape. Your two cards have the same shape and thus the same cD (very high). The difference in total drag is due entirely to the difference in size.

Do the experiment again with a 5x5 card and a 5x5 cylinder. The cylinder will exhibit less total drag. In this case, the objects have the same frontal area, so the lower total drag is entirely due to the cylinder's more efficient shape. Which is to say, it has a lower cD.

[ChrisB]

Talk about frontal area. A Boeing 747 has a Cd of .031!

The Elise and, in particular, the Exige are not slippery shapes. Lotus made a trade-off between drag and down force in favor of down force. It corners better, but not so great on the straights.

[robains]

Can't really debate much said, just don't know enough about the physics involved. But still doesn't seem like that is a good measure of drag -- physical reality of the size and shape of a Mustang GT front windshield is no where near as "slippery" as that of my S.

Does CD include the downforce greated with the air flowing up thru the nose into radiators? Can't believe that produces more drag than air hitting a perpendicular flat radiator in a Mustang GT. The Mustang GT also has NO undertray, plenty of odd drag inducing shapes for the air to find it's way around.

So what specifically is causing such a high CD?

Where's Adrian Newey when ya need him

xtn - yes you are correct (and no that didn't cause engine failure - that was 6 mo. prior to my car seeing a track).

[2-Y-CHROMOSOMES]

Phil, ever think about putting a LS1 throttle body on your setup ?

[Moto44]

I don't understand 95% of what is being discussed here, but it sounds very appealing. So, from a non-technical standpoint this is what I am interested in:

1. Is it likely that this would stress the engine and reduce it's longevity?
2. Would the extra horsepower/torque mean that other parts need beefing up?

[turbophil]

Originally Posted by 2-Y-CHROMOSOMES

Phil, ever think about putting a LS1 throttle body on your setup ?

I haven't, although maybe I should

Couple thoughts... are the LS1 TBs not all DBW? My old LS1 C5 was but perhaps those on the F bodies were cable operated---I can't remember and too lazy to google it?

I could certainly make it fit and tuning would be easy enough with the EFI to see if it makes a viable difference... Challenges would be the swan neck going into the blower (the next bottleneck). I've never looked to see how big one can bore the swan neck-- perhaps there's enough meat in that manifold to do something special. Sure would be interesting to try...

I know the stock airbox restricts airflow as I found on the dyno. Perhaps a monster TB would help it breathe even that much better...hmmmm....

I must admit that it feels good just to have the car out back together for 5 minutes after all the TVS R&D. My next step is to pulley down for more boost and see how high I can go before the charge temps get out of hand without an IC. I'm out of town starting tomorrow so I won't be making any progress on any Lotus stuff for at least a week, unfortunately...

That said, if anyone has a LS1 cable TB with IAC they want to send me so it's waiting for me when I get back, you're welcome to

Cheers,

Phil

[fzust]

1. Any time you increase horsepower you increase the engine stress and could reduce longevity. Small price to pay for countless hours of top-quality entertainment!

2. Yes. Clutch being #1. Valvesprings should be upgraded, but I would recommend that for anyone, stock or otherwise.

[turbophil]

Originally Posted by Moto44

I don't understand 95% of what is being discussed here, but it sounds very appealing. So, from a non-technical standpoint this is what I am interested in:

1. Is it likely that this would stress the engine and reduce it's longevity?
2. Would the extra horsepower/torque mean that other parts need beefing up?

Moto44-

Answer to #1 is always yes when it comes to power adders. Any SCer or turbo is going to shorten the engine life. The more power, the shorter the life, as there's simply more wear and tear (pressure) on the internals... Just a fact of engine life. That said, I doubt hardly anyone puts enough miles on their Lotus that the wear factor is truly a factor at all... Even if the B life of the engine was reduced by 50% (which I doubt it is), that probably wouldn't impact anyone much since it probably started with a 200 or 220K estimated useful engine life... Oncemore, let's say you did reach that point where compression has fallen to undesirable levels or you have some crazy catastrophic failure, these engines cost less than a custom taylored suit from Nordstroms to rebuild... Isn't the suggested engine life of a P GT3 only like 120 hours or something like that? And then fork over some serious bucks to rebuild. These little 4 banger yota mills are throw-away units........... I'm exagerating a bit obviously, but you probably get what I'm saying. Power comes with a price. The longest lasting version of the 2ZZ is the NA one...

2. Main part that needs help is the clutch. The rest of the car is OK to handle the power...

Best,

Phil


EDIT- Ooops! Fred beat me to it... Sorry for the duplication....

[Bavarian Motorist]

Originally Posted by robains

Can't really debate much said, just don't know enough about the physics involved. But still doesn't seem like that is a good measure of drag -- physical reality of the size and shape of a Mustang GT front windshield is no where near as "slippery" as that of my S.

Does CD include the downforce greated with the air flowing up thru the nose into radiators? Can't believe that produces more drag than air hitting a perpendicular flat radiator in a Mustang GT. The Mustang GT also has NO undertray, plenty of odd drag inducing shapes for the air to find it's way around.

So what specifically is causing such a high CD?

Where's Adrian Newey when ya need him

xtn - yes you are correct (and no that didn't cause engine failure - that was 6 mo. prior to my car seeing a track).

You would use the measurement of cd*A (frontal area) to measure the REAL drag of a car. And if you use the cdA unit, you'll find the Elise is not really that much more inefficient than a C6 Corvette.


Is it not true that downforce and lift have the same effect on drag?

[Purist]

The actual drag force is .5 * density of fluid * drag coefficient * frontal area * velocity squared.

Yes, down force and lift will both cause "induced drag" in the exact same way.

[turbophil]

A bit off topic from the threads, but good 'ol wiki has some answers: Automobile drag coefficient - Wikipedia, the free encyclopedia

Cheers,

Phil