NST Pulley Dyno Results

[richardholdener]

Here are the official results of an honest back-to-back dyno test of the NST pulleys (crank, alt & WP). Car was run on the dyno with stock pulleys and then we swapped out the stock pulleys for the NST (I believe 10% under driven) though sizing on WP and Alt looked the same. Pulleys were definitely worth some power as indicated by grpah. Note also the power numbers (123 wheel hp) is a new NA record-posted elsewhere with description of mods.

[pinoypizzaboy]

i have 10% underdrive set. so your intake+ longtube header w/ matching midpipe+ pulleys = 123 whp?

[mikenacarato]

very nice!

[richardholdener]

Plus Xd Tb and CAI (though we used a stock filter lid flipped over).

Originally Posted by pinoypizzaboy

i have 10% underdrive set. so your intake+ longtube header w/ matching midpipe+ pulleys = 123 whp?

[pinoypizzaboy]

Originally Posted by richardholdener

Plus Xd Tb and CAI (though we used a stock filter lid flipped over).

wowoweewa almost the same gains as the blitz sc. i might be purchasing the whole richard holdener collection if the price is right. (longtube header, intake, midpipe,) will the midpipe bolt on to tanabe axleback? or better yet i remember you talking about a low buck turbo kit back then

[WeSellCarParts]

Very nice to see a dyno. NST FTW! :)

[CASTREX]

Finally some back to back Dyno for the Pulleys!

This is probably one of the more popular mods for the Yaris. NST FTW!


Richard,

Correct me if I'm wrong but some of the benefits from the lightweight/under drive pulleys are not only the power gains (as show in your graph) but also the ability of spin the engine faster and therefore been able to get it faster into the power band?

Same principle as with a lightweight flywheel.

BTW, do you know that Fidanza has a lightweight Flywheel for the Yaris and for the xD. There is another option for the Yaris from SPEC. They run for around $300.
Have you considered throwing one of those into your combo?

Oh, and your observation is accurate the only under driven pulley is the Crank pulley. Is 10% smaller. The Alt and WP are same size as the OE.
NST has an underdrive pulley in the works for the xD as well.

[cali yaris]

way to go Richard, thanks for testing that!

question: would the gain the pulleys make be the same on a totally stock car, where the pulleys were the only mod?

[richardholdener]

This will get a little technical, but the gains from the under drive pulleys come not so much from the chnage in weight but from the change in accessory speed relative to crank speed. You are reducing the parasitic losses associated with driving the accessories. This is a function of the moment of inertia (MOI). Changes in MOI come from changes in weight and changes in diameter (of a rotating object). In the fomula for MOI, the changes in diameter are squared meaning they have much more of a change on MOI than changes in weight. Since you dealing with such a small gain from any change in MOI to begin with on a accessory pulley, the difference in weight has even less effect than a change in diameter (making a small crank pulley). This is why lightweight flywheels usually show little or no gain in power on a dynojet-they are not what is limiting the rate of acceleration of the engine (a change in tire/wheel diamter or weight will have much more of an effect on power than lightweight flywheel). Here is where things get tricky. Lightweight engine components do have an effect, it is just that they have more of an effect when the acceleration rate is increased (free reving the motor for instance) or when a drag race car (a real fast one) accelerates through the gears at a higher rate than can be achieved on a chassis dyno. What all this boils down to is that underd rive pulleys (meaning even larger alt and WP pulleys) will add power more than any change in weight and that a lightweight flywheel would add more power if you make it smaller in diameter, but you are not likely to register any gains with the flywheel on the dynojet. Hope this helps.

Originally Posted by CASTREX

Finally some back to back Dyno for the Pulleys!

This is probably one of the more popular mods for the Yaris. NST FTW!


Richard,

Correct me if I'm wrong but some of the benefits from the lightweight/under drive pulleys are not only the power gains (as show in your graph) but also the ability of spin the engine faster and therefore been able to get it faster into the power band?

Same principle as with a lightweight flywheel.

BTW, do you know that Fidanza has a lightweight Flywheel for the Yaris and for the xD. There is another option for the Yaris from SPEC. They run for around $300.
Have you considered throwing one of those into your combo?

Oh, and your observation is accurate the only under driven pulley is the Crank pulley. Is 10% smaller. The Alt and WP are same size as the OE.
NST has an underdrive pulley in the works for the xD as well.

[richardholdener]

The gains from the pulleys should be the same with stock motor since reduction in losses from accessories is the same.

Originally Posted by cali yaris

way to go Richard, thanks for testing that!

question: would the gain the pulleys make be the same on a totally stock car, where the pulleys were the only mod?

[ztrack157]

I'm banning myself from the site for 6 months or else I'll be broke.

[RagnaCaT]

What all this boils down to is that underd rive pulleys (meaning even larger alt and WP pulleys) will add power more than any change in weight

Hmmm? NST I hope your reading this we need BIGGER WP And ALT pulleys. If they came threw with the 10% reduction they could definetly come out with something like this!!! NST FTW! I'm glad I have a Yaris!

[pickledchang]

if you already have a 10% underdrive crank pulley, and then you install a 10% overdrive for your accessories, there may be adverse effects to running your accessories 20% slower. the miniscule hp gained probably wouldnt be worth dead batteries, dim headlights, overheating at idle, etc... NST may have already experimented with these.

[RagnaCaT]

But doesn't the overdrive compensate for whats lost with the 10% my corrolla did have an 18% reduction with 0 problems

[CASTREX]

Originally Posted by pickledchang

if you already have a 10% underdrive crank pulley, and then you install a 10% overdrive for your accessories, there may be adverse effects to running your accessories 20% slower. the miniscule hp gained probably wouldnt be worth dead batteries, dim headlights, overheating at idle, etc... NST may have already experimented with these.

That's correct.

With the under drive Crank pulley you are already under driven the system by 10%. The reason why NST did minus 10% instead of a 15% or 20% is because there is no compromise at that level for the components... If you have a race car and you don't care about those little things like AC/ radio etc... you can probably for a larger reduction.

Remember this is a bolt on part for every day use. If anyone wants special pulleys remember that NST DOES custom works.

[CASTREX]

Originally Posted by RagnaCaT

But doesn't the overdrive compensate for whats lost with the 10% my corrolla did have an 18% reduction with 0 problems

What over drive? For an over drive you will need a larger than OE crank pulley.

If you add a larger water pump and alternator pulley you are making those components run even slower!

[RagnaCaT]

Originally Posted by CASTREX

What over drive? For an over drive you will need a larger than OE crank pulley.

If you add a larger water pump and alternator pulley you are making those components run even slower!

Ok I had a concept all wrong since day one thanks for clearing that up for me

[richardholdener]

We have experimneted with different under drive ratios and there definitely is a point where the water pump speed is too slow for when you are stuck in traffic and/or the electrical system willnot charge at lower engine speeds. I think the 10% crank from NST works well-my point was more one of theory and not recommendation. For an all-motor race application, we will get rid of belt and drive WP electrically-thereby eliminating all losses asociated with accessory drive. Not really practical for street use.

Originally Posted by pickledchang

if you already have a 10% underdrive crank pulley, and then you install a 10% overdrive for your accessories, there may be adverse effects to running your accessories 20% slower. the miniscule hp gained probably wouldnt be worth dead batteries, dim headlights, overheating at idle, etc... NST may have already experimented with these.