Using a slower water pump (19 teeth vs 22 teeth)?

[PandaBear]

Car in question: 97 Acura Integra RS

The VTEC model uses a 22 teeth water pump and slightly longer timing belt compare to the 19 teeth water pump and slightly shorter timing belt. VTEC has a higher peak HP, higher redline, shorter gearing in transmission, and lower torque in lower rpm.

So it seems like VTEC model wants a slower water pump for this reason. Mine is a non VTEC model and I think I might be able to take advantage of a slower water pump to improve fuel efficiency. Would it be dangerous? I don't drive this car anywhere close to redline and since the engine temperature is thermostat regulated (fail safe thermostat) it shouldn't be a problem in non racing environment.

People who did LSVTEC (mixing the longer stroke rod/crank with VTEC head) have used both setup with no problem, so I'd imagine my lower power stock setup should be fine if I switch to a slower water pump. 22 teeth vs 19 teeth should make the flow rate and water pump drag 16% lower, probably translate into 1-2% fuel economy improvement.

 

[mechtech2]

Or, you could go to an underdrive crank pulley and get an improvement from all the accessories.
This is a common performance mod, and usually is the best HP per dollar you can get.
Downsides are slightly low voltage at idle, the and AC won't work as well at idle.
But doing the water pump alone is OK. It's odd that the high performance version uses a slower WP.

 

[IndyIan]

I assume most underdrive pulleys have more effect than that, I would guess you'll have no problems.

 

[dwendt44]

The 22 tooth pully is the slower one in this instance.
An undersize crank pully would also slow the water pump, if you can find one.

 

[willix]

The under-drive pulleys are protect the belt driven accessories from over revving first, that is the purpose and really offer little in ways of HP gains. But there usually pretty.

 

[Eddie]

Put it together as original. The perceived increase in efficiency won't be noticed.

 

[brandini]

Underdrive pulleys would be great, I have seen before and after dynos from project cars in well-trusted magazines (r&t/C&d) that gain hp & tq from them.

 

[PandaBear]

I don't plan to touch the crank pulley that drives the accessory system due to harmonic and vibration related issue. From what I understand the stock pulley is balanced for this reason, and I do like my AC cold in idle.

Thanks for the advice, on my next timing belt I'll try out the slower water pump and belt setup.

 

[javacontour]

In a competitive marketplace where more power (less loss) and better fuel economy helps sell cars, wouldn't Honda have already made this decision if they felt it met their goals for the car?

They've likely calculated how much airflow crosses the radiator at a given road speed and a number of other factors.

You want to change this to get a fraction of an MPG?

It may work. I think what you give up is some certainty compared to the factory engineered solution, some reserve capacity in the cooling system, and less cooling at higher RPMs.

You said it yourself, the VTEC engine has a higher RPM so it likely moves a higher volume of coolant at those higher RPMs. If you are crossing the desert headed to Vegas let's say, at high speed, are you sure the engine has sufficient cooling capacity using a water pump that may pump a lower volume of coolant?

Personally, I wouldn't mess with any of this unless you are looking to run this car on a drag strip, or enter some hyper milling competition.

But that's just my opinion. It's based on impression and preference, not fact, so take it for what it's worth.

 

[javacontour]

The other thing I was thinking of is what happens to the next owner when you sell this hybrid design and they go to replace the timing belt or water pump.

It may not be a big concern, but it occurred to me.

 

[willix]

+1 air cond a must.
http://www.goldeneaglemfg.com/index.php?main_page=product_info&products_id=818

 

[PandaBear]

Yeah, I do think that I'm giving up reserved cooling capacity by going to a slower water pump setup at the worst case scenario.

I'd imagine where the problem is will be at the full throttle low rpm scenario which I think will not be that big of a concern since I have an automatic that will downshift and unlock the torque converter in these scenario. This engine have the same pump speed/ratio regardless of automatic or manual.

One thing I do know, is the high performance version use a slower water pump to reduce drag due to the closer/shorter gearing and the higher rpm power band.

Not planning to sell this car, and even when I do, It'll be 270kM at the next timing belt job, so most likely I won't get rid of it until well into the 300kM, the last thing a buyer will be concerned is you use a different water pump than stock.

 

[willix]

I do think the T-sat will regulate flow accordingly and flow is not really comproimised. less effort is needed to spin the current 22t pump. The present 22 tooth turns slower like 10%-thats good.

 

[The_Jeff]

I wonder if you'll get better MPG by blocking off half your radiator.

Think about it: your water pump is trying to push coolant against your thermostat, if it's mostly closed the coolant has to go through the small bypass system, heater core etc.

If you warm up the radiator with some cardboard, the thermostat will be open wider, and more coolant will flow through the fat hoses and relatively wide tubes in the rad.

IMO this would do you as much good if not more so than an internal engine mod. It would at least tell you if you have cooling capacity to spare.

 

[PandaBear]

I looked up the bypass hose, it's big, bigger than the coolant hoses in and out of the radiator, and since the bypass hose is shorter and straighter, it will be less restricted than the whole cooling system throught the radiator.

My main concern is actually if it will confuse a mechanic. If the mechanic use white out to mark the spot on the old belt and transfer it to the new belt without checking the marking, and it becomes off by 3 teeth (since the T belt also needs to be 3 teeth longer), then I could get an engine that is stuttering, requiring a return trip (although it is not enough to bent your valve), or a mechanic that yell at me for buying the wrong parts and putting the old water pump back in and cause sloppiness of the system, etc.

If I do the belt myself, I'll of course be careful not to mess it up, but if you bring your car to a mechanic, you'll never be sure what kind of short cut he will take.

Blocking off radiator in California summer is not an option, you can really cause worst case issue.

 

[onion]

Sounds to me like a whole lot of trouble for nothing.

 

[mechtech2]

Underdrive pulley gains are RPM related, not throttle related.
For a small street car, expect 5-7 HP at 6,500 RPM.
A couple of HP when cruising.
But you can certainly feel the difference.

 

[Eddie]

+1 onion

 

[KrisZ]

Originally Posted By: onion
Sounds to me like a whole lot of trouble for nothing.


That's exactly what I was thinking.