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Mods for automatic

Joined
9 April 2003
Messages
150
Location
Miami
I'm looking into mods for my A/T nsx, and a fellow A/T owner recommended intake, exhaust, and stall converter. What is a stall converter? He runs low 12's now.
 
He is referring to a "torque converter"... In an automatic transmission, the torque converter plays the roll of the clutch. The inefficiency of the torque converter is a big part of what gives manual transmissions such a big advantage (assuming a driver that can shift quickly).

A torque converter has two primary characteristics: "stall speed" and "torque multiplier". The "stall speed" is effectively the RPM range at which the torque converter begins to multiply torque. The multiplier is, well, the multiplier. An example is that a 3500RPM stall torque converter with a 2.0 multiplier on a car that produces 300 ft lbs of torque at 3500RPM will produce 600ft lbs of torque at 3500RPM under WOT. The torque coverter itself is a mechanical fluid coupling so a basic understanding of mechanical concepts can give you the general picture.

http://www.tciauto.com/tech_info/torque_converters_explained.htm

All of that said... Level 10 makes torque converters for the NSX, but it doesnt seem like too many NSX owners have gone for it. Kind of interesting because this was BY FAR the best mod I ever did for my C5 Vette (followed CLOSELY by a change in gearing).
 
Thanks for the info. Someone who has gotten a torque converter for their A/T nsx please give me your opinion. Was it worth it, performance gains, where do I get one? Thanks.
 
Mark Basch has recommended against doing any power-enhancing mods unless you are upgrading the transmission.

Remember, there's a reason that they reduced the NSX power to 252 hp with the automatic...
 
Yeah, I've been corresponding with Autowave about installing a supercharger on my A/T. They said they talked to Comptech and one of their engineers said that a supercharger is fine if you also use a smaller crank pulley. But I've been hesitant to go with the SC until it becomes more common, and any problems are discovered from long term use.
 
If I had the 9 grand handy for the Comptech, I'd put it in my auto. If the tranny went, I'd just replace it. I'm very dubious regarding the whole "can't handle 290hp" argument. I just really don't believe that.

Either way, adding a more efficient TC shouldnt stress the tranny, I dont think... Literally everyone adds TCs and better gearing on LS1s.
 
Level 10 sells a performance auto tranny for the NSX for $3300... Of course you'd still need installation...

http://www.levelten.com
 
Take it easy with that car spookyp, some of us are waiting for you to turn it in at the end of the lease and we want it to have a good transmission. :)
 
spookyp said:
I'm very dubious regarding the whole "can't handle 290hp" argument.

The argument is actually that it can't even handle 270 hp, let alone 290.

spookyp said:
I just really don't believe that.

Then I encourage you to go ahead and put mods in your NSX with an automatic. Let us know what happens, how much it costs, and whether it was worth it. :D

Obviously, for those who don't care whether or not they end up having to spend the money for a new transmission, there's no issue...
 
Follow the logic... If it "can't even take 270hp" then what about the autos with I/H/E? That would mean that I/H/E is putting you right at the edge of the transmission tolerance. It's just hard to believe that Honda chose to use such a woefully pathetic and inadequate auto tranny that the difference between 252 and 270 would destroy it.

A lot of it, I'm positive, will come down to how you drive it. I've seen Vettes that were on the stock auto tranny that were well outside of that trannys supposed absolute limit hold up fine for years. On the other hand, I've seen stock tranny's go on a totally stock car. It's just ridiculous to draw a definite line in the sand and say "1 hp more than 252 and the tranny will explode". It just doesnt work that way with mechanical parts...

There's a big difference between what an auto manufacturer is willing to warranty and is disinterested in upgrading, and what the part tolerance really is.
 
I actually talked to Mark Basch about this and he told me that the simple I/H/E will be okay for the auto tranny. He did tell me that the supercharger on an auto is a big no no.

I believe the reason the engine is 252hp is a by product of tuning the C30A to better suit the characteristics of the automatic transmission.
 
spookyp said:
It's just ridiculous to draw a definite line in the sand and say "1 hp more than 252 and the tranny will explode". It just doesnt work that way with mechanical parts...

No, it doesn't.

Parts fail according to a probability distribution. And Honda does not want parts to fail - under warranty or even afterwards. They want to keep their reputation for reliable cars.

Suppose the probability distribution looked something like this:

252 hp: < 0.1 percent of transmissions fail within 50K miles
253 hp: 0.2 percent of transmissions fail within 50K miles
260 hp: 3.0 percent of transmissions fail within 50K miles
270 hp: 8.0 percent of transmissions fail within 50K miles
280 hp: 15.0 percent of transmissions fail within 50K miles
290 hp: 25.0 percent of transmissions fail within 50K miles
330 hp: 60.0 percent of transmissions fail within 50K miles

(Please note again that I am making up numbers here. Whatever the actual numbers really are, the chances almost certainly rise with horsepower.)

I can see how, with that type of distribution, Honda would limit the engine power to 252 hp.

Note that the transmission doesn't necessarily fail when you go from 252 hp to 253 hp. However, as power rises, the chance of failure increases.

Seeing these numbers, you might be willing to put a supercharger on, hoping that yours is one of the 40 percent that encounter no problems - and it very well might be. If the tranny fails, you pay thousands to fix it. With those odds, you might consider that risk worth taking.

Someone else might consider a 3 percent risk of failure - which is significant, if not probable (ask E46 M3 owners about a 3 percent risk of failure) - too much to take, and prefer to do everything possible to avoid a significant chance of incurring an expensive repair.

It's your car, and your risk. When you put mods on your car, the risk increases. And any failures caused by the mods are not covered under warranty.

Originally posted by RyRy210
I actually talked to Mark Basch about this and he told me that the simple I/H/E will be okay for the auto tranny.

So did I, and I thought he recommended against any power modifications, including the "simple" I/H/E.

Originally posted by RyRy210
I believe the reason the engine is 252hp is a by product of tuning the C30A to better suit the characteristics of the automatic transmission.

I have heard one or two others say this - and they have all been owners of automatic transmission NSXs. I have never heard this from Honda engineers. Maybe it's true... or maybe it's wishful thinking on the part of those owners.
 
Last edited:
Tony Montoya said:
That thread brought back memories. Wow the Forum Nazi got involved in that thread also.
Those auto guys sure have issues.

No kidding! That was when I still had my '95 NSX-T automatic.
 
As an owner of a 94 A/T I'd really be interested in hearing of a successful S/C addition to an auto. I heard Comtech is doing a couple of them right now. I looked into the Level 10 folks but got bad feedback about them on an SCCA forum. So I don't know what to think about those guys.

I love my auto tranny, but I'm dying for more power. If the Vette's can do it, why not Honda?
 
Kind of interesting because this was BY FAR the best mod I ever did for my C5 Vette (followed CLOSELY by a change in gearing).

Wow, I can't believe Ken didn't clobber you for that contradiction. He must be starting to slip as he gets close to that 10k post mark. :D
 
nsxtasy said:
I have heard one or two others say this - and they have all been owners of automatic transmission NSXs. I have never heard this from Honda engineers.

Has anyone heard anything from Honda engineers about this? If so, I'm curious!

In the absence of authoritative info, I think there is something to be said for the theory that they decided to readjust the cam profiles and tinker with the power curve to better suit the characteristics of the automatic transmission since the auto cars:

1) have different gear ratios
2) have a lower RPM limit (to suit the auto transmission)

There may also have been some thought that purchasers of auto cars would want more low-end power vs. high-end power. Notice that the low-end torque curve is a little bit stronger on an auto vs. manual 3.0L motor.

In fact I would not be surprised if the number of 252 peak HP was a result rather than a goal of these changes.
 
Quick as I am on my way to work...

I have driven a Comptech SC AT car. Still shifts @ 7200 RPM, just gets there quicker.

The tranny is fine, but the miles are at 21k on a 93. about 7k on the setup.

The owner is lead-footed, but takes VERY good care of the car/fluids/tune/etc.

There are no internal mods to the tranny that I know of. He also has E/H.

I will post more on the car later.
 
spookyp[/i] [B]this was BY FAR the best mod I ever did for my C5 Vette (followed CLOSELY by a change in gearing).[/B][/QUOTE] [QUOTE][i]Originally posted by hendu said:
Wow, I can't believe Ken didn't clobber you for that contradiction.

I don't know anything about the effect of gearing mods on a C5 Corvette.

hendu said:
He must be starting to slip as he gets close to that 10k post mark.

No, I'm just looking for opportunities to reply so that I can increase my post count. And thanks, hendu, for providing one. ;)
 
Ken... I agree with the theory of your reliability chart. That's pretty much what I was thinking also...

Oh! the contradiction was that the TC was by FAR my best C5 mod yet was followed CLOSELY by the gearing :D LOL... well, you get the idea ;)

nsxparts... cant wait for more info! :D
 
I think the big question is why would Honda make such a weak transmission for the auto. I have friends with A/T Supra Turbos pushing 500 hp on the stock transmission with absolutely no problems. Why couldn't Honda make the tranny stronger?
 
The best feature of the Supra is its over-engineering. The bottom end, tranny, injectors and even stock turbo were all engineered to take more load.

The NSX was finely optmized and runs close to tolerance. The auto tranny is a weak link, but it is what it is. There was no chance of Honda spending money to update it. Basically, the choices are risk killing it (like nsxparts' friend), or proactively spend the money to replace it...
 
Didn't LG install one of his custom turbo setups on an A/T?

Maybe the owner of that NSX or someone that knows him will chime in.

Edit: I read the link to that old thread....I guess that owner doesn't post here.
 
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