Would love some opinions on 4.55 R&P upgrade only

[ilya]

The deal is done. I will be putting in the Comptech 4.55 R&P soon and do the clutch at the same time. I came upon an excellent deal on a used one that I could not pass on.
I have read through the FAQ and also through all previous topics on the matter. However, there aren't too many impressions from people who have done the 4.55 upgrade only (without short gears).

After reading through the wealth of info, it was very helpful in helping me decide to do 4.55 only which is what I will most likely do. I would like the overall improvement without the trade off of short gears. In addition, both may be a bit extreme for me since I do a lot of highway driving as well.

I would love some opinions from anyone who has the 4.55 only (or has had and upgraded) and what kind of improvement I am looking at from a fun factor standpoint. The numbers in the FAQ are available and look great to me.
3/10s of a second to 60 is a HUGE difference and well worth the grand it cost me for the R&P. Doing this alone gives benefits all across the board without any losses at higher speeds (aside from top speed which isn't a concern).
I know the numbers. I want subjective.

Differences, pros, cons various people have experienced with this setup alone.
I will be doing this for sure. I'm just excited and am looking for more info and impressions in the meantime before I have the install done. Thanks

OK... BEGIN RANT
As a side note, I have been debating the accuracy of the table in the FAQ. It's a great estimate, but the baseline +20HP bothers me. Speaking from experience... I don't care how light the NSX is, adding only 20HP will not net a gain of .4 seconds to
60mph without ANY gearing changes as well.
Adding 20HP to a 2500lb car will not even do that in the real world. .4 seconds is the difference between a C5 and a Z06. The Z06 had 35 more HP, more torque, much more extreme gearing, larger tires, AND considerable weight reduction to pull .4 seconds from 0-60.
When someone can accomplish taking that kind of time off their car, that is quite an accomplishment. 4/10 of a second is a significant difference that usually requires quite a bit of effort or a lot more power.
That is the difference between a C5 and Z06, a 3.2L NSX vs. a 3.0L approx.

Not taking anything away from the rest of the table, but I just don't buy that adding 20rwhp can improve 0-60 time in the real world by .4 seconds. I have modified all my vettes and been around for many others. I have never seen, even with much lighter imports that weigh less than an NSX, see that kind of radical improvement from 20rwhp. It's just unheard of.
Could there be an error somewhere????

END RANT.

Just wanted to throw that out there, as that figure has been bothering me for a while.
Not that I wouldn't love to get an extra .4 seconds from an I/H/E mod.

 

[Carguy!]

ilya,

I am sorry I don't know much about the 4.55 gears.

I do have a point about the .4 seconds though. It is not possible to quote 0-60 time increases with horsepower without some additional info. For example someone might be able to say a stock '91 with 20 extra horsepower will improve 0-60 from 5.4 to 5.0 seconds. But to make a statement that adding 20hp reduces 0-60 times by .4 seconds can't be accurate. For example if I have a supercharged car that is running 4.0 seconds 0-60 and I add 20hp I probably won't even see 3.9 seconds. It is all based on percentages not times. If you increase your horsepower 15% you might see an improvement of about 10% in your 0-60 time based on available traction. The same can be said about weight, if you drop your weight 300 pounds on a Hummer you will notice a negligable increase in speed, but if you drop the NSX by 300 pounds you will see a more pronounced increase.

Of course with the horsepower and weight savings there are a lot of other variables that you need to consider, like where the powerband is based on your gearing and where you remove weight can help or hurt your traction for 0-60 times.

I don't think a good indication of a cars performance is 0-60 times as so much has to do with getting off the line. You would be hard pressed to get an NSX to beat a newer Porsche 911 Turbo to 60mph even if you mod the car to have a much better power to weight ratio, simply because with all wheel drive you are going to hook up much better in the Porsche.

This is one reason why your C5 to Z06 Comparison doesn't work. The C5 is faster than a stock 3.0L NSX 0-60mph. So the percentage increase on the C5 is greater when increasing the 0-60 time .4 seconds.

For example a car that runs 4.0 seconds 0-60's it would be a 10% improvement to run 3.6's. If another car that is running 8.0 second 0-60's would only a be a 5% increase to run 7.6's.

So I guess in most ways I agree with you that you can't quote horsepower increases that will give you a specific increase in 0-60 times.

 

[ilya]

Thank you for the insight. I've noticed it posted quite a bit on the forum that adding 20hp would bring the potential 0-60 down by .4 seconds, and it never registered as kosher with me. 0-60 improvements by gearing can be measured more accurately than measuring for additional power.
So I'm not crazy after all.

Your point is well taken. My C5 to Z06 comparison was just to point out how much was improved and changed for the Z06 to get that improvement in acceleration.

 

[Jason Weaver]

Ilya, Man what a great deal on the 4.55! A thousand bucks! Please give us some real world impressions. I agree .4 is a great advantage on the 0-60.....short of NOS probably the greatest acceleration for the money you can buy for our cars. Let us know how it feels. Imagine if you still had your bottle hooked up

------------------
Jason

 

[ilya]

***Imagine if you still had your bottle hooked up ***

Aww... man. What did you have to go and say that for? Now I'm wondering the same thing... ...

I'm still waiting on impressions from some of the members. I know some of you must have the 4.55 R&P w/ stock gearing???

[This message has been edited by ilya (edited 01 November 2001).]

 

[sjs]

I'm thinking your highway miles are not a factor with the "short gears" (not an accurate term in my mind. More like "close gears" at least through fourth.) Anyway, since fifth is the same either way, highway RPM won't change. Which means that the close gears are better suited to someone wanting a bit more zip through fourth but a quiet cruise in fifth. On the other hand, the R&P gives you better torque multiplying in all gears at all speeds, but at a price.

 

[sjs]

OK, that last post was a bit too simplified. If a stock gear is good to say 40, and a new R&P drops that to 35 at the same RPM, then in fact the new R&P yields more zip from 0-35, less from 35-40, then more again from 40 to the next shift point etc. relative to the stock one. But overall you should still gain to most speed points.

 

[sjs]

Originally posted by Carguy!:
ilya,

...I don't think a good indication of a cars performance is 0-60 times as so much has to do with getting off the line. ...

Couldn't agree more. Same for 1/4 mile runs and even peak HP readings. The concept of "Usable" performance is also an issue, such as how it pulls from a rolling start at various RPM etc. All of which is why a data-logging accelerometer such as the G-Cube is the only way to go.

 

[1BADNSX]

Originally posted by ilya:
The numbers in the FAQ are available and look great to me.
3/10s of a second to 60 is a HUGE difference and well worth the grand it cost me for the R&P.
OK... BEGIN RANT
As a side note, I have been debating the accuracy of the table in the FAQ. It's a great estimate, but the baseline +20HP bothers me. Speaking from experience... I don't care how light the NSX is, adding only 20HP will not net a gain of .4 seconds to
60mph without ANY gearing changes as well.
Adding 20HP to a 2500lb car will not even do that in the real world. That is the difference between a C5 and Z06, a 3.2L NSX vs. a 3.0L approx.
I have never seen, even with much lighter imports that weigh less than an NSX, see that kind of radical improvement from 20rwhp. It's just unheard of.
Could there be an error somewhere????

Yes, in your logic.

Begin rant!

First, you want to believe the 0.3 second improvement due to the R&P, but want to ignore the improvement due to horsepower, even though they come from the same computation.

Second, you believe that the 4.55 R&P will help the acceleration without impacting highway driving. Both the stock five-speed and the short-five-speed have the same fifth gear, therefore they will have the same high RPM with the 4.55 on the interstate.

Third, you compare a C5 to NSX for gaining 20 HP. The C5 is both slightly heavier and has a higher base horsepower than the NSX. Both circumstances reduce the effect of adding power.

Fourth, you ignored the most important comparison. The stock 3.0 vs 3.2 NSX. The added 20 horsepower of the 3.2 and 6-speed improve the 3.2 coupe 0-60 performance about 0.5 seconds (roughly 0.2 for the gears and the other 0.3 seconds for the less than 20 additional HP to the ground). If you believe the numbers due to the gearing, how do the real world 0-60 tests improve so much for the 3.2 NSX? Maybe 17 HP to the ground?

End rant!

Sorry to be harsh, but people tend to ignore physics when it comes to gearing or any other belief. The computations in the FAQ are not back of the envelope calculations. They are specific to the stock 91 5-speed and changes to this baseline. They are not generalities to by applied to any car.

To be open, the numbers in the FAQ were early calculations with some extra assumptions. Maybe we can get Lud to post the more accurate calculations performed for the third quarter 2000 issue of the NSX Driver. The newest table included actual dyno numbers which makes them more accurate and also includes more combinations with 1/4 mile times. But the new results don't change your horsepower argument any.

Unless you drag race your NSX or do street starts from a standstill, the 4.55 R&P doesn't gain you much and it certainly doesn't help on a road course.

Bob Butler

 

[Jimbo]

Bob,

I don't want to speak for Ilya, but I don't think he said, or thought, that the 4.55 gears would not impact highway driving at all.

When I read his original comment I got the impression that he was mostly concerned about 0-60 acceleration and understood that top speed and the higher engine speed would be affected.

Pure acceleration from a standing start notwithstanding, with the 4.55 gears, however, couldn't you say that for any given gear or MPH, that in general the engine will be turning at a higher RPM?

And wouldn't this and the fact that the VTEC range would be closer at hand (or foot) make for the improvement in fun factor he talked about.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
Looking for 76-79 Honda Accords

 

[sjs]

Originally posted by Jimbo: When I read his original comment I got the impression that he was mostly concerned about 0-60 acceleration and understood that top speed and the higher engine speed would be affected.

Actually, top speed would likely not be lower, you will just be turning more RPM at that speed and should get there faster.

Pure acceleration from a standing start notwithstanding, with the 4.55 gears, however, couldn't you say that for any given gear or MPH, that in general the engine will be turning at a higher RPM?

Yes.

And wouldn't this and the fact that the VTEC range would be closer at hand (or foot) make for the improvement in fun factor he talked about.

The whole VTEC range thing continues to be somewhat misunderstood. I figure a real sports car is designed to rev high. So, to me the big benefit of VTEC is the low RPM lobes that extend the power band down so I can pull across a wider range. Just a matter of perspective I suppose, but the point is, don't be so eager to limit yourself to "VTEC" range. Looking at it another way, you could say that the lower R&P narrows the VTEC range. (in terms of MPH per gear)

 

[JickedOut]

I have a 91 that I added the 4:55 without the short gears. It rules.. I can't understand why they did not stick these in at the factory.. Anyway I have been Autocrossing this year and had a chance to drive another NSX(95) without the gear same day,same race ,back to back..
His car has a slow lub and powerless second gear change.. My car hits hard and goes in second. I was always bothered with the car going from 1 to 2 ,not now. You will also get a better pull in 3rd...If you street race you got to have it..
I get a little bit of a whine from the gear but only at certain rpm's, I enjoy hearing it actually..

 

[sjs]

Originally posted by 1BADNSX:
Unless you drag race your NSX or do street starts from a standstill, the 4.55 R&P doesn't gain you much and it certainly doesn't help on a road course.

On these I disagree. The R&P helps where it helps based on math. That's from a standing start or rolling along in any gear. (See my earlier post for caveats) And the benefit on a road course is strictly dependent on the course, in terms of speed of corners and length of straights. It may be better in some areas and worse in others, but overall it is more likely to help than hurt. What makes you think otherwise?

 

[Jimbo]

"...When I read his original comment I got the impression that he was mostly concerned about 0-60 acceleration and understood that top speed and the higher engine speed would be affected..."

I should have been more specific. I only meant that top speed would be affected in that the speed would be less at redline.

Higher RPMs and less top speed at a given RPM in general.

My comment regarding VTEC was more in line with if you're driving around town, in general your RPMs will be closer to the start of the VTEC "fun" range.

I guess I don't see where the low RPM lobes really transform the NSX. Perhaps, I'm missing something, but for me the car is much more fun and responsive when I'm at higher RPMs. I mean, the NSX isn't a dog or anything, but 2,500 RPM in third or fourth gear isn't going to produce neck-snapping acceleration either.

Perhaps I can put this another way (for Ilya's benefit). I can drive around town in fourth gear and it's OK. But if I drive around town in third gear, then my car is much more responsive in general. Wouldn't 4.55 gears provide a similar analogy (if not the same level of difference)?

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
Looking for 76-79 Honda Accords

[This message has been edited by Jimbo (edited 02 November 2001).]

 

[sjs]

Originally posted by Jimbo:
[B...I should have been more specific. I only meant that top speed would be affected in that the speed would be less at redline.

Higher RPMs and less top speed at a given RPM in general.

My comment regarding VTEC was more in line with if you're driving around town, in general your RPMs will be closer to the start of the VTEC "fun" range.

I guess I don't see where the low RPM lobes really transform the NSX. Perhaps, I'm missing something, but for me the car is much more fun and responsive when I'm at higher RPMs. I mean, the NSX isn't a dog or anything, but 2,500 RPM in third or fourth gear isn't going to produce neck-snapping acceleration either....
[/B]

Yea, I knew what you meant. It’s just that over the years I’ve built engines that reved to 8k and pulled hard from 5500, but naturally they were really useless at anything below that. As I said, a car like the NSX is supposed to perform as it does at high RPM, which is all you see after first gear when racing, whether in a drag race or road course because you keep it in the right gear to accomplish that. So, with or without VTECH the NSX would have to run strong from 5k – 8k. After all, it’s a sports car not a Vette.

Running strong at high revs is a given, drivability below that is not. That’s why for me the beauty of VTECH and similar technologies is that they make a high-reving sports car as easy to drive as a Camry when you are not racing. Go drive some of the old Ferraris and such and you’ll see what I mean.



[This message has been edited by sjs (edited 02 November 2001).]

 

[ilya]

Wow. Sorry guys. I didn't want to start an argument over here.

The main point of my post was for some opinions on the 4.55 only upgrade and impressions.

A lot of great insight on my 'rant'.

I didn't mean to come across as stating that table was wrong. I was questioning the +20hp improvement because it did not, and still does not, seem right to me.

The reason I don't question the gearing numbers, is because I have seen (and done) gears in the past, and those kinds of improvements are standard. Gaining between 2 and 4 tenths of a second at initial speeds is expected with an aggressive upgrade like the 4.55 and/or shorties. Upgrading my differential in my C5 did exactly that. So when I look at the numbers, I see a standard improvement that I have seen with vehicles in the past.

Then I see the HP improvement. And from my experience, I have never seen anything gain that kind of time from a mere 20hp with no other changes. So naturally, I was inclined to question it. I am not trying to say that it's undeniably false. It just did not seem right to me, which is why I brought it up... so I can see what other people think about that.

People speak of the vette as if it's this heavy monster that weighs several hundred pounds more than an NSX and that comparisons are invalid. The C5 weighs just over 3200lbs., no more than 3250. Adding 20hp to that car, with no other changes, will get you .1 seconds improvement, if even that.

I think I was misunderstood. I did not mean to compare a C5 to an NSX. They are different cars, with different weight, suspension, gearing and torque. I meant to compare a C5 to a Z06. This is the same car with weight reduction, more power, more aggressive gearing, and better tires.
I pointed out HOW MUCH had to be done to a C5 hardtop to get that kind of real world improvement in times. A Z06 IS a C5 hardtop, with all the changes I mentioned. General consensus among enthusiasts: C5 0-60 4.7
Z06 0-60 4.3. That's .4 difference and a HUGE one, gained my mass improvements to the entire vehicle. If you have driven in both, it is obvious that a C5 is tame compared to a Z06. Very big difference.

So a car with 350hp and 375 ft/lbs of torque, that only weighs 3250 lbs, required the following to cut 0-60 time to .4 seconds.
1. Over 100 lbs of weight reduction
2. More aggressive differential and
gearing (in fact, a completely different
gearbox)
3. An additional 35 horsepower
4. Larger tires


So you can see where I am coming from when I question that a mere 20rwhp can gain that same improvement on a car that only weighs just over 100 lbs less.

Now I am not saying it's impossible. I am just saying it does not make sense to me. That is why I posted my thoughts. I can see it on a motorcycle, but not on a 3100 lb. car. I also believe that the .5 sec improvement for the 3.2L NSX has almost EVERYTHING to do with gearing (and additional torque) and less to do with 20 more horsepower (flywheel no less).

This is just a perspective from someone who has done these mods in the past and understands realistic expectations from additional HP. If there is a fatal flaw in what I am saying, by all means explain it to me. Explain to me how the NSX can see such a radical improvement with such a simple HP change while other cars of similar weight and power do not. I never say that my word is final and I understand there are others that know much more than me on the subject. But I have been there and done that, and seeing that kind of number immediatley brings up red flags... for good reason.

 

[sjs]

ilya,

For what it's worth, if someone asked me how much difference +20hp at the flywheel would improve 0-60 times in an otherwise stock 3.0 NSX, I'd guess a lot less than .4 seconds. Like you, I have experienced over the years that it takes a lot of extra HP to get a small reduction in ET. Of course a major factor is where you get the power. If it's in the higher revs at the expense of torque in the mid range, then your gain in 0-60 and 1/4 mile might be less or even a loss. But even with a well distributed 20 bump in the curve, I'm surprised that the calculations suggest several tenths to 60.

 

[ilya]

Jickedout, Thanks for the impressions. I'm really looking forward to it.

I'm glad some people agree where I'm coming from.

Anyone else with only 4.55 gears that can chime in? I need to find someone in my area for a ride.

BTW, I had a chance to take a ride in the final single turbo while I was down at NSX Modified today. Final meaning it was done with tuning and boosting at the right levels and revs. It's a stock 5 speed, but
it pulled like a raped ape and I'm still smiling.

The blowoff valved sounds nice too.

Since he will be giving rides at the next two meetings here, maybe everyone who had a ride can post their impressions. It would be good to add a lot of different opinions and give this thing some legitimacy.
He also showed me the brackets he is fabricating into the tubing. This will allow the entire thing to be removed as one piece when the engine needs to be worked on.

[This message has been edited by ilya (edited 02 November 2001).]

 

[sjs]

Originally posted by ilya:
It would be good to add a lot of different opinions and give this thing some legitimacy.

It's always fun to hear how perception measures up to reality, but you need the reality for legitimacy. Doesn't someone amongst you have a G-Cube? A few minutes with that in each of several cars back-back will tell the truth, the whole truth, and nothing but the truth.

Do I need to come up there and organize this?

Hey, that's not a bad idea! I should be able to get a decent airfare. Can anyone pull strings on a place to stay?

 

[ilya]

I don't have any connections for hotels, but you're always welcome at my place if you're down here. I like meeting club members from around the country.
Three other NSXers (Andrie, Chris (SOS), and 1 other person) will be down in 2 weeks for the Pahrump track event and we're going to get together afterward. That's the week of the meeting in Calabasas I think.

 

[1BADNSX]

Originally posted by ilya:

Explain to me how the NSX can see such a radical improvement with such a simple HP change while other cars of similar weight and power do not.

Your comparison to the C5 has four differences that compound to make a significant difference.

1. The C5 has more power compared to the NSX. The newest calculations were done based on actual dyno data for a stock 91 NSX with max power of 235 HP to the road. I don't know the actual C5 road horsepower, but I estimate it to be 287. Therefore adding 20 HP to the NSX is a 8.5% improvement, while it is only a 6.97% improvement in the C5. This by itself is 22% better for the NSX.

2. The C5 weighs slightly more. My calculations for a 91 NSX used (3000 lb car + 200 lb load) 3200 lbs. Using your quote for a C5 of 3250 lbs plus adding a 200 lb load would yield 3450 lbs. Adding 20 HP to the C5 would be transmitted to a larger mass(20/3450=0.058), compared to the NSX (20/3200=0.0625) -- reducing the effect of additional horsepower on the C5.

3. As Carguy pointed out earlier, improving a C5 0-60 time from 4.7 to 4.3 is a 8.5% improvement in acceleration. While increasing the 91 NSX time from 5.56 to 5.16 is a 7.2% improvement and easier to accomplish.

4. I am not certain, but some of the earlier posts may have assumed the 20 HP addition is at the crank, it is not. It was assumed at the wheels at the max power point and a linear proportion at all other areas of the RPM band.

These four factors compound to make the effect of an extra 20 HP less effective on your C5 example.

Originally posted by ilya:

I also believe that the .5 sec improvement for the 3.2L NSX has almost EVERYTHING to do with gearing (and additional torque) and less to do with 20 more horsepower (flywheel no less).

It is very hard to change what somebody believes. Some people still believe the world is flat. But you are dead wrong saying the acceleration improvement to 60 mph in the 97+ coupe is more to do with the gearing than power. The 97+ has the same R&P as the 91's and the only difference in gearing below 60 mph is 2nd gear. The 6-speed 2nd gear is almost the same as the short gear set, and both will gain about 0.2 second improvement 0-60 mph. The additonal 17 HP to the ground (20 at the crank) accounts for the majority of the acceleration improvement.

On seperate subjects:
- JickedOut is correct, the 4.55 would help autocrossing. But, I am not sure why he is also not running the short gears since he has to run in a prepared or modified class and his stock gear set will still have the dreaded RPM drop he mentioned shifting into 2nd gear.
- sjs is correct that the 4.55 could help or hurt you depending on the road course, but I disagree with his final assessment that "it is more likely to help".

Bob Butler, PhD
91 NSX Red/Black
97 M3 (BMW Club Racer)

 

[JChoice]

I've thought about doing this for some time.

According to the charts, isn't it safe to say that the 4.55 R&P is the one change will help in nearly every way except for top speed?

 

[JickedOut]

The reason JickedOut does not have the short gear set is that the money tree he planted in the backyard is fresh out of cash...

When I was talkin about the dreaded RPM drop going into 2 this was BEFORE I installed the 4:55. My car hits hard in 2 and pulls strong through the gear..
I don't think I will ever buy the short gears,my gearing seems fine now..

Drive a car with the 4:55 around a autocross track,then take a stock gear car around a lap... This will clear all your thoughts and you will just know you want the 4:55...

 

[Jimbo]

Bob,

Minor quibble. You're under-estimating the weight of the NSX and over-estimating the Vette.

The C5 Corvette (removable roof) weighs 3221.

The NSX-T (removable roof) weighs 3164

The C5 Z06 (hardtop) weighs 3115.

The NSX (coupe/hardtop) weighs 3070.

For the removable roof version, the Vette weighs 57 pounds more.

For the hardtop/coupe the Vette weighs 45 pounds more.

The Vette still weighs more, but it's nowhere near 250 pounds heavier of a car. Fairly impressive, actually for a steel chassied, V8 car.

-Jim



------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
Looking for 76-79 Honda Accords

 

[NSXocto]

I've even heard some say that doing both the short gears and the 4.55 was almost too much.

So... If you could do one or the other? Would it make more sence to do 4.55 or short gears.

Is there any more wear-and-tear on car, one way or the other?

Hey JickedOUT
Now that you have the 4.55 what are your speeds, shifting 1st to 2nd and to 3rd in strong VTECH range compaired to before you put it in? Can you give us some idea?