6-Spd 1991 NSX vs. 6-Spd 2001 NSX Questions...

[hdsr5]

Hello. I have a 1991 Acura NSX with a 2001 NSX 6-Spd Transmission, ARC Induction Box, Comptech Headers, Comptech Test Pipes, Taitec JGTC Parallel Exhaust, DALI Racing ECU Mod, and Comptech Stage 2 Clutch w/Lightened Flywheel. How fast do you think my car is on the 1/4 mile & 0-60, and how would my car fare against a stock 97-01 NSX & a similiarly modified 97-01 NSX? I know most 97+ NSX's are Targa's, so does the weigt difference let me have an advantage even though I have 20 less HP stock and .2 less liters? Would I be up & up with an identically modified 97+ targa? Hardtop?

 

[nsxtasy]

We can speculate (and I will do that in a moment), but the only way to know exactly how your car, with your mods, performs would be to test it, on the dyno and/or the dragstrip.

Magazine testing of bone-stock '97-01 NSXs typically have the NSX-T doing around 4.8-4.9 0-60 and around 13.3 1/4, whereas '97-01 NSX Coupes are generally 2-3 tenths less, with one test (Car and Driver) having a '98 NSX Coupe as low as 4.5 and 12.9. If your car has a similar power profile to a 3.2-liter with a 6-speed, and if it has similar weight to a 3.2-liter 6-speed coupe, then I would expect its performance to be similar, too. But those "if"s are assumptions.

 

[BladesNSX]

Hello. I have a 1991 Acura NSX with a 2001 NSX 6-Spd Transmission, ARC Induction Box, Comptech Headers, Comptech Test Pipes, Taitec JGTC Parallel Exhaust, DALI Racing ECU Mod, and Comptech Stage 2 Clutch w/Lightened Flywheel. How fast do you think my car is on the 1/4 mile & 0-60, and how would my car fare against a stock 97-01 NSX & a similiarly modified 97-01 NSX? I know most 97+ NSX's are Targa's, so does the weigt difference let me have an advantage even though I have 20 less HP stock and .2 less liters? Would I be up & up with an identically modified 97+ targa? Hardtop?

Hey hdsr5

Can we trade?

With all those mods you have you should fair well with most other cars on the road. I'm sure you would out perform (straight away) stock or slightly modified '97 or newer NSXs assuming the drivers are equally skilled. It really doesn't matter though as long as your happy with your car. Why don't you dyno or track test your car like Ken says. See if you can hook up with a '97 NSX owner for the test and compare.

 

[hdsr5]

Does the fact that I have .2 liters LESS displacement affect my torque and/or acceleration, or does the performance gap between the 3.0 & 3.2 liter motors diminish as you add on power parts. What EXACTLY is it that makes a 3.2 NSX so much faster than a 3.0? I have been trying to get my car to the point where I can compete with and possibly beat a 3.2. If a 3.2 was modded EXACTLY like my car, how would the race go theoretically?

 

[nsxtasy]

Does the fact that I have .2 liters LESS displacement affect my torque and/or acceleration

Yes, because that's what you're starting out with...

does the performance gap between the 3.0 & 3.2 liter motors diminish as you add on power parts.

Yes, it diminishes.

What makes a car go fast is (a) the amount of force applied to the rear wheels (wheel torque), which is a function of engine torque and gearing (horsepower is also a function of engine torque, and takes gearing into account), and (b) the weight to which that force is applied, and (c) the amount of grip that your tires have on the road. If your car, with its mods, applies similar power to similar weight using similar tires, then you can expect similar results.

What EXACTLY is it that makes a 3.2 NSX so much faster than a 3.0?

It's the fact that it produces more horsepower and torque, not just the amount of displacement. If your car, with mods, produces as much horsepower and torque as a 3.2, then it should be as fast as it would if you had the 3.2.

If a 3.2 was modded EXACTLY like my car, how would the race go theoretically?

Theoretically, if the 3.2 made exactly 20 hp at the crank more than your car, and the mods to the 3.2 added exactly the same hp and torque as your mods, and if both cars weighed the same, then the 3.2 would still have exactly 20 hp more than your car, and it (the 3.2) would be faster.

As a practical matter, the same mods are not always available for both engines, and they won't necessarily give the same benefit to both engines.

Why don't you put a supercharger on yours? That should make it faster than a stock '97-01 3.2-liter NSX, which seems to be your objective...

 

[hdsr5]

WOULD a 97-01 NSX have 20 more HP then me with the same EXACT mods, or would we have about the same HP figures. What would be each car's HP figure (roughly) if they both had the mods I do? All the parts I have are available for the 97, except fo rthe chip. WOuld that additional mod push me over?

 

[Paul]

Hdsr5,

I have a 91 with CT headers, CT exhaust, and a drop in K&N. I have some other mods, but as far as straight line performance that's all I got.

I recently purchased a new 6-spd for my car but before I installed it I wanted to see what the car would run with the above mods and the stock 5-spd. I put the stock 15/16 wheels back on the car, took the trunk mat, tools, and spare tire out, and ran the car with a quater tank of gas. Here in Houston (at sea level) with the above mentioned mods, weighing in at 3060 with driver, I was able to turn a 13.02 @ 108.89.

The same night we had a 2000 NSX-T with us on stock 16/17 wheels having only a bolt on RM exhaust, otherwise stock. He turned 13.1x @ 106.xx. His car weighed in at 3340 lbs with driver (he has no weight reduction done to his car).

I ran my car only one other time when I first purchased it. I ran it completely stock and turned a 13.54 @ 104.5 (first time ever to the track).

I plan to run the car again someday now that I have installed the 6-spd. I hope to drop my time into the high 12's while keeping the same mph.

So to maybe help you answer your question if you are racing a STOCK 97+ NSX-T with your current mods, you should be faster in a straight line. With the mods you have you should be putting down about 265 at the wheels. Stock 97+ cars usually put down around 260 at the wheels. So with the same transmission (6-spd), less weight, and a little more hp, you *should* be able to beat a stock 97+ NSX-T.

If a 97+ NSX-T has similar mods as yours, that would even things up. The 97's and up have a much better header design than the pre 97 cars. Bolting aftermarket headers onto a 97+ car does not net the same rwhp gain as it would on a pre 97. With similar mods though, the two cars should have about the same rwhp. At this point (I think) it would depend on the driver and how much weight reduction each car has. This would make for a much closer race.

Another question you had was about the increase in displacement. It appears that the 0.2 increase does not help increase power output that much. I only say this because I have seen 3.0L motors with aftermarket exhaust and headers dyno about the same as stock 3.2L motors.

The new factory header design and the 6-spd appear to make more of a difference than the 0.2L increase in displacement on the 97+ cars.

Hope this helps.

Paul

 

[nsxtasy]

I plan to run the car again someday now that I have installed the 6-spd. I hope to drop my time into the high 12's while keeping the same mph.

According to Bob Butler's calculations, changing from a stock '91 5-speed to a 6-speed will reduce 1/4 mile time by 0.11 second.

The new factory header design and the 6-spd appear to make more of a difference than the 0.2L increase in displacement on the 97+ cars.

Well, I'm not sure how you can separate the effect of the header design from the effect of the increase in displacement, but again according to Bob's calculations (which closely mirror actual test results), you will get roughly four times the acceleration improvement by adding 20 hp than you would by changing to the 6-speed. (Extrapolating from his work that says adding 15 hp reduces 1/4 mile times by 0.32 second.)

 

[hdsr5]

With 265 HP @ the wheels in my car and assuming I take nothing out of my car and I have 18/19 Racing Hart M5 rims, as well as the fact that I weight 165 lbs and installed a dvd deck & amp in my car which add a little weight, what should my trap speed be around, if my engine were running good and was "healthy"?What would the fastest 1/4 mile time I could run be if I were to drive it as is on the track? I want to know what I should run when I DO run to compare. How much faster would I go if I took out the spaer tire, tools, and all mats.

 

[nsxtasy]

what should my trap speed be around, if my engine were running good and was "healthy"?

Given your unique set of mods, you would have to take it to the drag strip and find out for yourself. It would be difficult for anyone who doesn't have a car configured exactly like yours to gess how much faster it is with the power mods, how much slower it is due to the bigger heavier wheels and tires, etc.

What would the fastest 1/4 mile time I could run be if I were to drive it as is on the track?

If you drove it on the track (like a man ), you would find out what its lap times are. If you are looking for 1/4 mile times, take it to the dragstrip (like a kid ) and find out for yourself.

How much faster would I go if I took out the spaer tire, tools, and all mats.

Spare tire = 29.4 pounds
Tools/jack = 17 pounds
Floor mats = 6.4 pounds

Bob's calculations show that a 100-pound weight reduction reduces 1/4 mile times by 0.16 second, so removing these items will reduce 1/4 mile times by 52.8 percent of that amount, for a reduction of about 0.08 second.

 

[sjs]

Bob Butler's calculations are OK for relatively small increases and approximate results on a normally aspirated engine, but take them with a grain of salt and common sense beyond that.

For example, if 15hp lowers ET by 0.32 seconds, will 150 hp drop it by 3.2? The stronger BBSCs have that much power gain but certainly aren’t running 10s, and that’s not just a matter of traction. Another notch up are David and Gerry with 500+ which would put them into serious single digits! In other words, it’s not a simple linear calculation. There are several decent low cost performance simulation programs available that take all the major factors into account.

Of course another important factor is the shape of the power curve. Simple bolt-on mods like IEH don’t drastically change the shape of the power curve, but power gained from a turbo tends to start earlier and therefore has a greater impact on times & trap speed.

Frankly your questions are too much for anyone to answer accurately without a good simulation program. If you really want to know the answers spens a few buck on this or something similar:

http://www.cartest2000.com/

It even has several NSX's pre-defined!

 

[nsxtasy]

In other words, it’s not a simple linear calculation.

No, it's not. However, it is likely to be very, very close to a simple linear calculation when used for interpolation between known data points (e.g. 100 pounds results in X change so 50 pounds results in half of X) rather than with gross extrapolation by an order of magnitude (e.g. ten times more than the figures that were calculated) such as in the example you give. Common sense says that it is reasonable to extrapolate by just a third more than the difference that was calculated, as I did when going from 15 hp to 20 hp, but not by ten times more than the difference that was calculated, as in your example. I am quite certain that re-doing the actual calculations for the data points in question would show that the results are virtually identical to the interpolations and slight extrapolations made above.

 

[sjs]

No, it's not. However, it is likely to be very, very close to a simple linear calculation when used for interpolation between known data points (e.g. 100 pounds results in X change so 50 pounds results in half of X) rather than with gross extrapolation by an order of magnitude (e.g. ten times more than the figures that were calculated) such as in the example you give. Common sense says that it is reasonable to extrapolate by just a third more than the difference that was calculated, as I did when going from 15 hp to 20 hp, but not by ten times more than the difference that was calculated, as in your example.

I know Ken, but many people may not. It is a near certainty that someone would think "cool, so if I get a turbo or SC..." and crunch some highly flawed numbers, so I figured I would caution them.

 

[NeoNSX]

nsxtasy; i have a stupid (but serious) question after reading your 2nd post. If you have two cars with same HP/torque/weight, and one has larger wheels than the other car (eg. 16" vs 18") will the car w/ larger wheels necessarily get better times?

If so, which factor would be more important: more thread on the road, or the larger diameter?

 

[nsxtasy]

nsxtasy; i have a stupid (but serious) question after reading your 2nd post. If you have two cars with same HP/torque/weight, and one has larger wheels than the other car (eg. 16" vs 18") will the car w/ larger wheels necessarily get better times?

If so, which factor would be more important: more thread on the road, or the larger diameter?

Remember first that wider tires don't put more rubber on the road. They change the shape of the contact patch by making it wider (side to side) and narrower (front to back), but the size of the contact patch doesn't change, since it's a function only of the weight of the car and the air pressure in the tires.

Some people claim that wider tires provide better handling, but any such differences are very slight. There are several significant disadvantages to larger wheels and wider tires, including greater weight (and remember, it's unsprung weight, so it's more important than general weight), poorer effective gearing (if the outer diameter is larger), etc.

All the (several) tests that I've seen conducted by magazines show that lap times generally improve slightly when going from 15" to 16", stay roughly level to 17", and then get worse when going to 18".

 

[NeoNSX]

<B>nsxtasy</B>... ahhhh....*the penny drops* ... this makes more sense now; thanx.


i've always been led to believe that larger wheels mean a greater spread of rubber on the road meaning more HP can be turned into forward motion.

i've read lots of comments on prime about larger wheels effecting handling, but only wondered about their effects on gearing (never read anyone complain about gearing though) ... so you've answered another question i've always had.


Sorry to sound like a newbie, but i don't think i fully understand "unsprung weight" of the wheels. Do you mean because the wheels are underneath the car & not 'assisted' by suspension? Either way i don't get why it's more important than typical weight (except that the NSX-intro video went on about how the OEM rims are 50lb less ).

...so am i right in saying larger wheels (18"+) are mainly cosmetic and have little impact on performance? (oops! i shouldn't post that ... might start a flame war... ) This is the view i've had for a long time.

thanx for your help; no wonder you're the nsx-guru. back to hdsr5 and sjs ... i don't want to digress this thread away from your conversations.

 

[huckster]

geez ken, everytime i think im smart, you go and post something like THAT!!!

i havent seen 'extrapolation' since grad school. I've got to use that in my next corporate memo. I really love pissing them off and making them get out a dictionary. One of my little joys.

On a serious note---seems like ive read that the contact patch stays roughly the same irregardless of tire size? I can see the potential truth of that during cornering, but what about linear acceleration? and if so, Why/how? Seems like vehicle weight relative to applied torque/hp would potentially allow for use of much bigger tires/contact patch. ie. drag racers?

enlighten me oh wise one

 

[huckster]

what exactly is meant by contact patch? a wider tire does mean a wider contact patch, no?

i understand why cornering contact patches are limited irregardless of how big the tire due to weight/force applied unequally, creating a smaller patch carrrying heavier load(compared to linear contact patch).

more info please?

 

[nsxtasy]

The contact patch is the area of the tire that is in contact with the ground. Assuming no vertical g forces acting on the car other than gravity, the total area of the contact patches can be found by dividing the weight of the car by the air pressure in the tires.

You can read more about the contact patch on the Tire Rack's website here, including a pretty good illustration of the difference in shape of the contact patch on a wide tire and a narrow one.

On a serious note---seems like ive read that the contact patch stays roughly the same irregardless of tire size? I can see the potential truth of that during cornering, but what about linear acceleration? and if so, Why/how? Seems like vehicle weight relative to applied torque/hp would potentially allow for use of much bigger tires/contact patch. ie. drag racers?

During cornering, there are lateral (side to side) forces acting on the car but not vertical (up and down) forces. This means more weight is on the outside tires, and less weight is on the inside tires. The outside corner patches are larger, and the inside ones are smaller. The total weight is the same, though. Same thing for acceleration, when the weight shifts from the front to the rear, shifting the size of the corner patches.

Vertical forces can act on the car such as when you crest a hill and the car gets light. This can reduce the size of all four contact patches, but only for a moment; once the car settles, it's back to 1 g vertical force of gravity.

 

[1BADNSX]

Bob Butler's calculations are OK for relatively small increases and approximate results on a normally aspirated engine, but take them with a grain of salt and common sense beyond that.

Of course another important factor is the shape of the power curve.

If you really want to know the answers spens a few buck on this or something similar:

http://www.cartest2000.com/

It even has several NSX's pre-defined!

Since my numerical computations are in question, an explanation is in order. The calculations for the NSX Driver article were specific to the NSX (actual dyno numbers, aero drag, gearing .....) and I don't think they would be improved by buying an off-the-shelf product.

The quoted 15 HP figure was at peak and it was assumed that the power was 6.4% higher across the RPM range. I chose 15 HP because this seems to be the average difference between the 3.0 and 3.2 engines from my experience. If my memory is correct, I even added the cases of 97 coupe and T in order to compare them directly with changes to the 91-94 coupes, and a separate computation for the 95-96 T's.

I agree that extrapolation of any results can be dangerous, but you would be surprised by how precise the results can be interpolated and even added like linear functions.

Bob

 

[Smoothaccel]

During cornering, there are lateral (side to side) forces acting on the car but not vertical (up and down) forces. This means more weight is on the outside tires, and less weight is on the inside tires. The outside corner patches are larger, and the inside ones are smaller. The total weight is the same, though. Same thing for acceleration, when the weight shifts from the front to the rear, shifting the size of the corner patches.

Vertical forces can act on the car such as when you crest a hill and the car gets light. This can reduce the size of all four contact patches, but only for a moment; once the car settles, it's back to 1 g vertical force of gravity.

Nsxtasy, as always you got me thinking. Whan accelerating, the weight does shift from the front to the rear. And that is one forces acting on the tires (contact path). But how about the rotational force. The force that the axle puts on the tires that makes it want to compress under heavy rotational torque. What do you think happens to a wider tire versus a narrow tire? Is it safe to assume that the wider tire has a greater potential for holding on to the road.
P.S I dont think that very wide and heavy tires will reduce 1/4 mile times but i think that there is an optimal tire width for the power because a heavier wheel does slow down the car quite a bit.

 

[sjs]

Since my numerical computations are in question, an explanation is in order...
Bob

I wasn't questioning them so far as they went, but I don't think they hold up very well if simply extended on out. Existing cars seem to back that up. Of course with large increases there are other factors involved such as the possibility of an extra shift, but even then they look very optimistic.

As for the cartest2000 product, don't underestimate it until you try it. It has a dizzying number of parameters factored in and is much more accurate than I would ever hope to be through manual calculations. And as I said, it already has several NSX models defined which can then be modified to match a real car. It's not the best simulator out there, but it may be the best for the money.

 

[nsxtasy]

But how about the rotational force. The force that the axle puts on the tires that makes it want to compress under heavy rotational torque. What do you think happens to a wider tire versus a narrow tire? Is it safe to assume that the wider tire has a greater potential for holding on to the road.

No. During hard acceleration (which is what you're talking about), the main factor for traction is the size of the contact patch (which is not affected by the width of the tire). Drag racers let air out of their tires to increase the size of the contact patch. And they use slicks, not because they are wider, but because they are a very soft, sticky compound.