Any particular reason you are using a dual mass flywheel? (no standard flywheel/torsion disc?) Those things are heavy and have huge inertia.

 

So, it's not just a clever name then. I don't think that's his car, so he probably can't answer that in any case.

Back on topic- on the matter of coolant recirc- I know the LT1s do that, but how about the LSx? I"m not up to speed on that. The older small blocks dead-head against the Tstat until it gets hot enough, so you have very little flow until the Tstat opens.

And for me, I'd spend $300 on the things that net more than 4hp first, before I got to that. Plus, electric pumps make me nervous- probably unfounded, but it seems like added complexity for little gain.

 

Electric water pumps made me nervous at first but I don't think twice about it now as so far, the two I've owned have been quite reliable. No....it wouldn't be my first choice for doing mods, but you can only do so much until you run out of things to do. Same for the friction and thermo coatings.

 

Cheat just a tiny bit as after my SS was stolen, I bought a Collectors Edition LT4 C4. Was very comfortable with the LTx technology vs LSx technology. That may have been short sided thinking.

The transmission is different vs an F-body and if you use a lighter single mass flywheel the trans rattles in neutral. Just getting old n cranky not caring for the noise having two billet flywheel assemblies sitting in my garage set and ready to bolt in if needed. Plus I hear all about hp gains from aluminum driveshafts and lighter flywheels, but so far I’ve not seen them on the dyno.

 

Ya I know the transmissions are different, I guess they never made a single flywheel with a traditional disc that has the damper vs. the flywheel. Since it rattles there is no damper in the disc then.

I know a good amount about most 'Vette manual setups since I used to work for the company that made the stock clutch/disc's, more familiar with LT1/4/5 and LS1/2/7 setups. I was never able to info for the ZF trans if they made a traditional style setup. I know they only offered a dual mass setup for the LT5, so I guess more than likely no traditional setup was made fro ZF.

If you think those are big and heavy you should see the ones for the diesel truck they make, holy crap they are like 100 lbs.

I know the feeling, I can't stand the rattle in my car. I know it needs a new disc for sure.

 

They still rattle even with a sprung disc when using a single mass. It's the nature of the beast due to the main shaft/ counter shaft spacing, or something like that. Also means they're stronger the most. Very reliable tranny and much under rated. Expensive to repair/rebuild as well.
Scott

 

I usually run out of money before I run out of things to do like $300 water pumps.

My T56 rattles a little in neutral- always has since I bought it new in crate. I'm running a factory LT1 clutch and a 35lb billet flywheel (that's all there was in 1995 ).

I think the less mass thing helps a lot more in the lower gears. If you're running a dyno at 250rpm/sec accel rate, it won't show like it would at 600+rpm/sec. Driveshaft mass is so close to center, that it doesn't add much inertial load, so the benefit is minimal. Of course, that didn't stop me from spending $150 on a 5.0 aluminum shaft, just to see if it would work. Fit like a glove.

 

The drive shaft may not have a large radius for inertia, you have to remember it is much longer than a flywheel and all of its mass is contained at the outer radius. Where as a flywheel will have more evenly distributed mass, WRT radius and its mass is more close to its center. What are typical weights for flywheels and driveshafts? Then we could figure out easily what has more inertia.

Actually I think less inertia helps in higher gears where your mechanical advantage is smaller than in lower gears. Lower gears = more torque.

The bigger reason though not to get an aluminum driveshaft is that farther away from the engine, inertia has less effect on torque/rpm acceleration. The easiest way to see it it that the farther away from the engine you have mechanical advantages (i.e. trans gear ratio, differential gear ratio, and then tire/wheel sizes). Although if you are looking for overall weight reduction, then every little bit helps.

Thats what seems to be the norm around here, although OEM replacements are junk compared to OEM originals. OEM originals take out all gear rattle in operating RPM's, or else people at FORD, GM, etc. really get mad.

 

Had my 97 SS dealer fitted with the optional aluminum driveshaft vs the steel one and immediately went to the dyno and got zero gain. In swaping from a single mass flywheel back to the dual mass in my C4 there was zero loss on the dyno in going to the heavier one.

One of those who thinks you really have to watch and deep think about what ya read as hey I read stuff to, but then put it to the test under independent controlled conditions to verify the results. There are a bunch of scammers out there trying to get your money in my opinion. Was really bummed about the driveshaft, hopeing to pick up 3-5 hp from what I was reading. Man, I was hyped!!

 

Wow, I would expect to see a difference.

On our bike engine at school took out 2 gears and shaved down 2 others and saw an average of 2%-5% increase across the torque curve with a peak around 12%. Maybe the loading dyno has an effect?

I can't figure out what I'm missing.

 

Don't forget about the heater hose lines- they are quite often the way of recirculating the coolant through the engine prior to the thermostat opening.

 

It's likely the opposite. I know that for my car, the stock 2.75" steel shaft was about 16lbs, whereas the 3.5" aluminum one was just over 8, IIRC (I have notes, but not on me). On my flywheel, the majority of its mass is far from center, not close. If I had to give a percentage, I'd say that 65-70% of a flywheel's mass is out in the area of the clutch disc surface. To me, there's no question that a flywheel puts a far greater inertial load on the engine than the driveshaft, due to the distance of the mass from the rotational center.
That doesn't surprise me, especially with a 4th gear pull. If you pulled again in 2nd gear with the two weights, I'd expect to see something- probably not huge, but something. Inertial loads matter more the faster you try to spin the engine up.

Unfortunately, I've forgotten how to calculate all this.

Surely, some of the big boys here that do dyno work have experience with this?

 

[QUOTE=Todd80Z28;4564638].
That doesn't surprise me, especially with a 4th gear pull. If you pulled again in 2nd gear with the two weights, I'd expect to see something- probably not huge, but something. Inertial loads matter more the faster you try to spin the engine up.

QUOTE]

Common sense says a lighter weight will be easier to rotate and what you’re saying makes sense. Being nothing shows up on the dyno in 4th gear, I'd also believe it would be minimal at best in lower gears but some consequence should be evident. However there is also a stored energy effect that may make a car actually quicker upon launch and changing gears. For both reasons a heavier flywheel doesn’t bother me but I don’t have objective track data to substantiate that statement. My launch rpm’s did change with different flywheels, but not sure if the car went slower, faster or to check the box that says: None of the above.

My issue is and always has been being I'm a consumer, aftermarket companies promoting false gains with conjured or irreproducible data. At least with the water pump you see reproducible gains pretty much across the board.

Plus if you believe David Vizard, the ideal temperature for making hp is 170 degrees. With a 160 thermo, the fans programmed to come on just over 160 degrees and the electric pump, my personal car stays pretty close to 170 most of the time. Even after a hard run in 70-80 degree ambient temperatures it rarely goes over 176-178 and then recovers quite quickly.

My sheetmetal intake with a substantial air gap may be helping some plus the car has an enlarged air intake, but I'll take anything you can get. Two thumbs up for electric pumps in my movie rating.

 

Not normally, unless its a truck with the heater return back to the radiator tank itself. Normally the heater hose plumbs back into the coolant crossover jacket which then routes the coolant through the thermostat and out the waterneck.

SBC's have a coolant bypass on the passenger side water pump leg that recirculates the coolant back into the block until the thermostat opens.

 

But this isn't true, mount a 2" diameter tube that weighs 2lbs and a 10" diameter tube that weighs 2lbs and see what is harder to spin.

Basically inertia is based on some percentage of weight and the square of the radius for round items spining about their own axis

Example:
Inertia of tube about its own axis = mass * radius^2


So, for an equivalent mass making the radius larger makes it hard to turn, a la inertia.

Right, Torque = Inertia*rotational accerleration

But not only for distance from rotational center but also due to gearing in the transmission. You have effectively increased your torque (say 2.5 times roughly for first gear) where as you only reduce your weight by 0.5 times. I think its safe to say gearing has more bearing on the inertia in the driveshaft/axles than the inertia.