Jonesy's NSX Build Thread

[redrocket265]

The problem with the NSX is its a 90 degree v6 that requires significantly splayed journals to run smoothly. Compare our crank with the m3 crank in the picture. Which one looks simpler (and therefore "stronger" all other things being equal)?

Fun story, the reason that M3 crank was on the balancer that night was because a few days prior during testing we broke the crank that was in the car, and had to put in a new one, haha. To be fair to the crank, it had a rough life - 100k street miles followed by two trips up Pikes Peak before being turned into a race-winning endurance car...but, at any rate, I've seen firsthand more inline 6 cranks break than NSX cranks

 

[Blazed.]

wow nice build! :wink:

 

[jones83]

Sorry for the late feedback on the build. This week has been hectic to say the least. Anyway, the crank was sent off to the machine shop to get double checked and rebalanced in the event that it needed it. Halston, the machine shop owner who Wil uses for balancing cranks and other things explained to Wil about how his new balancer has some newer tech that saves individual bob weight and this and that. Without giving out too much info that is proprietary between what Wil does during a build and what Halston does during his process everything was rechecked. Max rpm that we expect to spin the motor to is 8200rpm due to stock cams and stock valvetrain. So first Wil rechecked the weights on all the parts again by himself to make sure everything checked out and to make sure that there is linearity between all common parts. Wil sent the new rechecked weight measurements to Haslet and it was off to the races again to get the crank rebalanced.

IMG_9767 by Jones
IMG_9768 by Jones
IMG_9769 by Jones
IMG_9770 by Jones
IMG_9771 by Jones
IMG_9772 by Jones
IMG_9773 by Jones
IMG_9774 by Jones
IMG_9776 by Jones

Haslet worked on the balancing and after the final spin had the crank way under tolerance without the need for Mallory, in this case. With the suggestions that were presented in the thread Wil wanted to double check everything to make sure he was either correct or catch a possible mistake and get it correct. Even though the balancing worked out in the end to be ok Wil wanted to say that he appreciated those that brought up the concern in the first place. You never know when you can be wrong and learn something new.

The crank is back at the shop and Wil should be back working on getting the block together soon. I know the rebalancing messed with some of the scheduling he had set working on the car and others currently in the shop. As soon as he is able to get the block back together he said he would take more pictures of everything and the charger mocked up.

 

[Mac Attack]

You're moving right along now.... Did the machine shop ask for your clutch to do an external balance too?

My rotating assembly (except the ATI harmonic dampener of course) was balanced together with my old carbon fiber clutch, and it was sooo smooth when I took it to 9k RPM on a few occasions.

But, RPM stands for ruins peoples motors, so I keep it to 8k redline these days for engine longevity.

 

[redrocket265]

Did the machine shop ask for your clutch to do an external balance too?

Nah, clutch/flywheel should be (and are) neutral balanced. The crank shouldn't be balanced with the flywheel/clutch, unless you want to rebalance the crank every time you change your clutch/fw.

As far as higher RPM, I'd be fine spinning this bottom end up to 10+, the difference is up top. If the valves can't retract fast enough they're gonna still be hanging out down low when Mr. Piston comes up, and you'll have a lot bigger problems than a li'l OOB-misfire. Spring the valves for as high an RPM as the cams will make power, anything more than that just winds up making it more work for the engine to open the valves and you start losing power.

 

[Operator]

I have build two CP-Carillo C30A engines and both needed mallory. Carillo rods/cp piston set is 90 grams heavier than OEM titanium. It does not make sence if mallory is not needed !
20 grams of balance at 7000 rpm is about 100 kilos 117 times / second. We are spinning these engines over 8000 and bot engines had plenty of kilometers . 20000 km and 40000+ km .
But mayby you are right . And i hope at you are right ! It is easy to check how much Honda crank was over or under balanced . Just bolt OEM "bobweigh" and spin.
Nice build !

 

[Mac Attack]

Nah, clutch/flywheel should be (and are) neutral balanced. The crank shouldn't be balanced with the flywheel/clutch, unless you want to rebalance the crank every time you change your clutch/fw.

You're right - it isn't practical obviously when you go to change the clutch....

That's why it's a good thing to check while everything is apart for at least one clutch (which should last a looong time if you choose the right clutch for the application) . If the clutch is perfectly balanced from the manufacturer and the interface with the crank is perfect, then nothing will need to be done. However, if you're chasing that last bit of perfection, you should always check the rotating assembly balance as a whole (obviously without the harmonic dampener).

Honda balances the NSX-R engines that way, along with all of the engine builders I know.

If you're willing to take a chance machining crank journals to within 0.0001" so you can use all same-color bearings, I just thought maybe this crank was externally balanced too. No biggie. We all have different philosophies in what we think is important or not given our past experiences and limited funding. Well, at least I know my funding is certainly limited.

And for the record, I changed out my CF clutch after 6k miles because I didn't like it.:biggrin: Fortunately, I know that there was no material removed from the crank to do the external balance for that clutch (as there shouldn't be theoretically). There was however, a small bit removed from the clutch flywheel when I had it balanced.

As far as higher RPM, I'd be fine spinning this bottom end up to 10+, the difference is up top. If the valves can't retract fast enough they're gonna still be hanging out down low when Mr. Piston comes up, and you'll have a lot bigger problems than a li'l OOB-misfire. Spring the valves for as high an RPM as the cams will make power, anything more than that just winds up making it more work for the engine to open the valves and you start losing power.

A few of us here have spun the stock valvetrain up to 9k without issue. The limit is the oil pump, but I engineered a dry sump system. You can still make power if you massage the heads a bit and use a different intake manifold. I saw no reason to change cams or valves for my build... just new OEM springs, retainers (because those two are highly stressed), seats, and seals. I didn't even need to replace the valve guides - there was no wear even at 120k miles!