Different pulleys - how much does it help?

[gran racing]

Alright, with the discussion of if we should allow crank shaft pulleys in IT, I need to ask how much do aftermarket pulleys help? I realize that it may help in acceleration from a start, but what about when at higher speeds? Do you notice a difference using different pulleys? (Not just talking about crank shaft pulleys)

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Dave Gran
NER #13 ITA
'87 Honda Prelude

[Quickshoe]

While reducing the speed of the accessories may save HP the primary benifit for many of us is the reduced speed of the accessories.

Keep in mind that our cars' stock cooling systems had to be adequate in stop and go traffic combined with low rpms and high ambient temps.

[Geo]

OK, technically low mass components don't add hp. However, they do spin up faster, leading to quicker acceleration that will show up on an inertial dyno as a hp increase.

On the SR20DE engine found in the Sentra SE-R and NX2000 they are known to "add" around 7 hp at the wheels, give or take a hp. This is a repeatable, documented gain under controlled testing.

A really good friend of mine is an engineer for Nissan and he claims 90% of this "gain" is due to changing to the low mass main pulley.


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[Greg Amy]

George, I find that extremely hard to believe. 7 hp? No way. Our own dyno testing does not suggest that at all; maybe a couple on a good day.

For the Nissan SR20DE, the biggest advantage is slowing down the water pump and power steering pump. The SR20DE has a very big problem with coolant cavitation at the water pump at high RPMs, and is susceptible to near-hydro lock at times. Further, the power steering fluid gets literally beaten to death, getting so hot that it deforms and almost melts the power steering lines.

Since there was never a non-power steering NX2000 or Sentra SE-R, we gotta run it (and we replaced our lines with stainless-braided Teflon.) To accomdate the water pump we found that the Nissan Stanza pulley was larger and *almost* fit, so we modified it to slow down the water pump (but it could really use some more...)

GregA

[Geo]

Originally posted by grega:
George, I find that extremely hard to believe. 7 hp? No way. Our own dyno testing does not suggest that at all; maybe a couple on a good day.

Have you dyno tested the full set?

These results have been reported from multiple people. It's not a one-time dyno glitch.

Originally posted by grega:
For the Nissan SR20DE, the biggest advantage is slowing down the water pump and power steering pump.

It's certain a big advantage, but there is a hp advantage.



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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[Greg Amy]

<font face=\"Verdana, Arial\" size=\"2\">Have you dyno tested the full set?</font>

"The full set" of what? We've dynoed it with all accessories DISCONNECTED and it didn't make significantly more horsepower, maybe a couple due to the reduced drag of the water pump and power steering pump. It only takes a couple of ponies to run those accessories in ANY car.

I strongly suspect these guys you are referring to are using a DynoJet for "horsepower" testing. The DynoJet is wholly dependant on measuring the acceleration of the drivetrain, which is strongly influenced by rotating mass. We do our testing on DynoPacks, which are hub-mounted (eliminating friction, rolling resistance, and rotating mass issues with tires and wheels) and works against a hydraulic load that can be adjusted to control the rate of acceleration (further reducing issues with rotating mass).

In fact, we have a running joke at the complex where the race shop is; when someone comes back bragging about a dyno run, we ask them if that scale was in "horsepowers" or "DynoJets".

http://www.melfab.com.au/dynopack/

Please be careful tossing around numbers like that; it may mislead ITAC and CompBoard members into inaccurate assumptions and incorrect decisions...

GA

[Geo]

Originally posted by grega:
"The full set" of what? We've dynoed it with all accessories DISCONNECTED and it didn't make significantly more horsepower, maybe a couple due to the reduced drag of the water pump and power steering pump. It only takes a couple of ponies to run those accessories in ANY car.

So.... You didn't install an aluminum main pulley eh? Your argument makes zero sense. The debate going on is about replacement main pulleys.

Originally posted by grega:
I strongly suspect these guys you are referring to are using a DynoJet for "horsepower" testing. The DynoJet is wholly dependant on measuring the acceleration of the drivetrain, which is strongly influenced by rotating mass.

Did you even read my first post in this thread or are you just choosing to ignore it. I already prefaced my response that low mass components do not technically add hp, but they spin up faster which shows as hp on an inertial dyno.

Originally posted by grega:
Please be careful tossing around numbers like that; it may mislead ITAC and CompBoard members into inaccurate assumptions and incorrect decisions...

Greg, I have done nothing to mislead anyone. Low mass pulleys (mainly the main pulley) will spin up faster. It does have an effect beyond reducing the rpm of the accessories. I think my post does more to inform. Don't even try to convince me that all the underdrive pulleys do is reduce accessory rpms. It's absolutely not true. And that my friend is the point.


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[Geo]

A big oops here. I went back and reread my second post and I did say there is a hp advantage. This is wrong. The engine will spin up more quickly and thus accelerate more quickly, as if there were more hp.

My apologies about the confusion and my apologies to Greg. I created the confusion myself.


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[Greg Amy]

<font face=\"Verdana, Arial\" size=\"2\">...And that my friend is the point.</font>

No, George, that's your point. My point is I want to stop cavitating my engine coolant and melting my power steering hoses, but I can't because of a stooopid Improved Touring rule that is being supported by hearsay, superstition, and witchcraft/pixie dust.

GA

P.S. My apologies to those that may find the items in italics redundant...

[Geo]

Originally posted by grega:
No, George, that's your point. My point is I want to stop cavitating my engine coolant and melting my power steering hoses, but I can't because of a stooopid Improved Touring rule that is being supported by hearsay, superstition, and witchcraft/pixie dust.

But it's not witchcraft and pixie dust. Low mass components accelerate faster than stock parts. There is another consequence to allowing alternate main pulleys if we allow removal of the harmonic balancers.

You can go on and on and try to discredit me because I talked about the "gain" in hp, but the effect of a full underdrive pulley set on acceleration with a SR20DE is the same as if we did add 7 hp.

This topic is not as simple as some would have us believe.


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[This message has been edited by Geo (edited May 07, 2004).]

[Banzai240]

Originally posted by Geo:
This topic is not as simple as some would have us believe.

I don't think it's as complex as some would have us believe either...

Simply put... some would benefit, and some wouldn't... Just like EVERY other allowance in IT. 7hp isn't going to bring the IT world to a screeching halt, and, once again, I'll go back to my standard line...

...I doubt that 90% of us actually have the ability and talent to utilize the difference in the first place...

I think this change makes sense, and it would be simple to put wording in to restrict those whose pulleys happen to be integral with the balancer from replacing them, if that's really an issue...



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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX

[Geo]

Originally posted by Banzai240:
7hp isn't going to bring the IT world to a screeching halt

No, but it is a big number given the currently restrictive IT rules.

Originally posted by Banzai240:
I think this change makes sense, and it would be simple to put wording in to restrict those whose pulleys happen to be integral with the balancer from replacing them, if that's really an issue...

I don't think it does make sense. Why do we suddenly need to do this? It's not like the ECU issue that was unpoliceable. IMHO it's rules creep that is unnecessary.

The complexity comes in the question of what exactly do we allow?

1. Either the main pulley OR the accessory pulleys as was requested?

2. All pulleys?

3. Only main pulleys that are not integral with the harmonic balancer?

4. Either main pulleys (must leave the H OR the accessories?

5. Change all the pulleys, but the harmonic balancer must stay?

It is more complex because there are many scenarios here. What exactly do we do without ending up with serious unintended consequenses?

As for me, full pulley sets are readily available for my car, so from a personal level, I couldn't care less. A set of pulleys is a drop in the bucket compared with a lot of the things I'm allowed.


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[Banzai240]

I'm likely to step on my own <insert bodypart here> with this comment, but far be it for me to resist a chance to step on my...

These are race cars... not SS cars, not T2 cars, but Improved Touring Race cars...

We don't go get groceries in them, and they aren't required to be driven to the track...

We are already allowing EVERY other pulley to be changed, except the ONE pulley that would eliminate the need for the others to be changed. For many, it would be simpler, cheaper, and more readily available to change the one pulley as opposed to all the others...

Every kid over the age of 16 has already done this to their cars... They spend this money on the pulleys before they bother to spend the money to paint over the crappy bondo jobs that they did trying to attach the body-kit that their buddy took off of the tuner they stole the other night...

This reminds me of the coil-over shock rules... "you can do this, just as long as you do it in the most round-about way possible..."

If the idea is to allow people to slow their accessories down, then let's give them the option to do it in the most STRAIGHT-Forward manner possible... This is a pretty straight-forward, bolt-on solution... I believe that any "unintended consequences" will be minor, and will be far outweighed by the intended ones...

Just my opinion, of course...

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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX

[Geo]

Originally posted by Banzai240:
These are race cars... not SS cars, not T2 cars, but Improved Touring Race cars...

I see. So next we will allow any cams, a return to remote reservoir dampers, big brake upgrades? Hey, they're race cars.

Originally posted by Banzai240:
I believe that any "unintended consequences" will be minor, and will be far outweighed by the intended ones...

Perhaps. But like the ECU rule, I think this will stir things up. First we will have to decide which scenario we will allow (see above). Then, some cars will benefit and some will not. Some will benefit more than others. And everyone will bitch (except those who benefit most).

Hey Greg, what do you think of allowing alternate main pulleys, but requiring you to retain the stock harmonic balancer? How about you Darin? Yours is also integral to the main pulley IIRC.

As I said, from a purely personal standpoint, I don't much care. Replacing one more pulley won't add much to my budget. I just think when the dust settles there will be people who will be really sorry we changed (assuming we do). I'm not sure that's such a good idea.

Besides, how many people are blowing up engines because they cannot change the main pulley?


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[Quickshoe]

I don't believe it will change much on the dyno.

But what if an unintended consequence is cars that are not rpm limited because of valve train can now spin that much tighter and not worry about cavitation?

An additional 2-7 HP for everyone (but the rotary) doesn't concern me as much as someone being able to spin the motor another 400-600 rpms (numbers pulled out of my arse). Maybe it doesn't make any more power at all, but now they have the opportunity to run a little lower gear w/o hurting top end.

This is a rule that won't have the same effect on everyone. I don't think we need any more of those than we already have.

[Ascona1973]

FWIW, on a GT-4 engine, on an engine dyno (not chassis), I saw a 4 hp hp increase @ 7800 rpms. I suspect this is because I reduced the water pump speed by 38%, and the alternator speed by 22%. On this particular engine, 8000 rpms can't be run continuously with stock pulleys due to the cavitation, the water temp increases drastically.

Bob

[jlucas]

Originally posted by grega:
The SR20DE has a very big problem with coolant cavitation at the water pump at high RPMs, and is susceptible to near-hydro lock at times. Further, the power steering fluid gets literally beaten to death, getting so hot that it deforms and almost melts the power steering lines.

Sorrry for the OT reply.... I don't know for sure about Nissan pumps, but other P/S pumps I've seen can be disassembled and some of the pump vanes removed. Hopefully that helps. Also for the water pump I just read something this weekend on this engine building page, http://www.theoldone.com/articles/badtothebone/
(search for the word vanes), which talked about trimming the water pump vanes. No first had experience with this one.

Jeremy Lucas
Team Honda Research
Kumho-Cobalt-Comptech

[This message has been edited by jlucas (edited May 09, 2004).]

[lateapex911]

Originally posted by jlucas:
...P/S pumps I've seen can be disassembled and some of the pump vanes removed. Hopefully that helps....
Jeremy Lucas
Team Honda Research
Kumho-Cobalt-Comptech

[This message has been edited by jlucas (edited May 09, 2004).]

It may or it may not, but it isn't close to legal.

I'll leave it at that.



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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[jlucas]

Originally posted by lateapex911:
It may or it may not, but it isn't close to legal.
I'll leave it at that.

Sorry, not an IT guy. I knew it's out for SS but I figured you IT guys would have some more latitude.

[MMiskoe]

Greg Amy - email off line if you are still having power steering over heating problems. Your Nissans & my Nissans run similar pumps, I don't have problems.

Sorry for the thread interruption.

Matt

[email protected]