j9fd3s

ok, i'm bored, but thinking tuning.



previously i'm leaning toward the load based dyno (the kind that lets you hold an rpm, and vary the load), i'm thinking this lets you tune every part of the map, and it also lets you stabilise at a given rpm and load, and you can find things like peak torque and maybe detonation/saftey



which is all lovely, but nobody drives like that! especially race cars



so maybe the dynojet is a better. or more realistic choice?

RX7 13B 4 UR AZZ

pure race car dynojet is fine IMO

but for a street warrior that has to have some streetability = load based IMO



Im going to set up my 86 for street/strip so i will be looking for a load dyno

Maxt

There has been alot of internet chatter about dyno differences, and talking with other dyno operators they have said yes there is a diffence between dyno readouts..

I think in a turbo car it will affect where you make your max boost and where your boost threshold is, since the dyno's do load differntly, although peak power should end up somewhere close since by that time the turbo should be at full boost, in other words the curve may change shape but overall number should be close..

I know from my own testing, on a n/a car, there is no difference, my p-ports initial dyno runs on a mustang dyno pegged it a 200.0, when I ran it on my dynojet, with the same tune, it read 200.1 the power curve was within decimal points at all times of the mustang dyno readout.. The dynapack is a little stingy, as I have seen dynosheets from car owners who then ran on the dynapack, see anywhere from a 5-10% loss... I know when the tuners in Japan compare numbers they correct the numbers depending on if the numbers are bosch or dynapack produced, which are the 2 most popular there.. They say there is a huge difference between those 2 dyno's.. So much so they say a 400 rwps dynapack car will be faster than a 550 rwps bosch dyno car.. The wonder of the dynapack is the fact its bolted to the hub, there is no strapdown tightness factoring, wheel slippage etc etc, it shows the smallest change in the tune, and the real time torque read out is what makes it "the tuning dyno". I if could afford a 100k I would have one..

As for load testing, pretty all dyno's now have some sort of load control for testing, the newer dynojet has eddycurrent instead of air brakes, mine's an older 248x so I have the proportional air brake control but it still works ok, as long as the tach signal is good.. You can hit every point on the map with a dyno, and keep it sustained there to really dial it in, in.. Road tuning is pretty difficult to get a full tune off of. After I got my dyno running and played with some cars I had done just road tuning on , I was suprised by how narrow the road tune was, I think its the odd time you hit those out of bounds areas on the maps that was never tuned by general road tuning, that blows motors.. A wierd gear change or unusual load change will do that..

With the dogmission in the car once I hit peak boost I, never dropped off of it, where as the stock transmission, I always started off each gear generally in vaccuum, I had to retune just for the gear change, as I was now at 20 psi after every gear change, regardless of what rpm it was at..

TYSON

Your car does not have the same inertia as the dyno roller, so your boost/load vs RPM will not always happen the same way.



Since the dynojet is generally in 4th, you might make 20 psi my 5000 RPM when starting from 2500 RPM for example, but starting from 2500 RPM in 5th you might have 20 psi by 4000 RPM.



Accelerating uphill in 4th would give you different boost curve than accelerating on the dyno in 4th, and what are the chances the dyno has the exact same inertia as your car, so accelerating in 4th on flat ground might not even be the same!



If the dyno has more inertia than your car you're covered, but with heavier street cars that might not happen.



I think if you've got to start from scratch with no good base map you need more than just dynojet pulls in 4th to cover all the conditions, otherwise you're just guessing.

Maxt

You just manipulate the braking to change the loading of the dyno, then you can hit every cell on the map, you use the dynatrac software with the proportional braking to lock the car into whichever rpm band you want.. 3rd gear tends to work better on the dynojet with rx-7's for Wot pulls, just so the speeds and brake temperature doesnt get out of hand..

j9fd3s

yeah, i left foot brake a little on the dynojet too.



hmm, so neat, they both work then

heretic

Ideal are the dynos that will accurately duplicate the load on the engine so the engine smoothly accelerates at the correct rate.



And then they also tilt the engine at various angles to simulate G forces...