Underdriven Crank Pulley question
02-03-11, 11:14 AM
#1
Hail Dented 7
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Underdriven Crank Pulley question
Hi, need some guidence. I have used a few of these on other cars and liked the results. Now on the RX7 is this mod actually worth it. I can get a used racing beat pulley from a friend for 20 bills. Though looks brand new. Would it be a good first mod? The car is not a daily driver, I use it from time to time, only in the summer months, drive it all of 1-3K miles a year, if that. No city driving I live in a really rural area and never any stopped traffic.
How involved is the install on this? Anything I should watch out for? I also noticed on the installation directions that I would need to get a different belt for this, not the normal one. Why is this?
For 20 bills I didn't see why not, but before I go ahead and get it, it would be great to get some opinions.
Thanks for any input you could contribute.
How involved is the install on this? Anything I should watch out for? I also noticed on the installation directions that I would need to get a different belt for this, not the normal one. Why is this?
For 20 bills I didn't see why not, but before I go ahead and get it, it would be great to get some opinions.
Thanks for any input you could contribute.
Last edited by VermontRX7; 02-03-11 at 11:16 AM. Reason: added some info
02-03-11, 12:07 PM
#2
meh
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from racing beat:
Racing Beat's Aluminum Main Pulley-Single Sheave for virtually all 1974-92 12A and 13B engines reduces the water pump/alternator drive ratio substantially to avoid water pump cavitation and alternator damage due to the extreme RPMs encountered in racing. It also reduces the engine's rotating inertia and the power loss to the accessories. The pulley is provided with a series of engraved timing marks at 0 degrees (TDC), 12.5 degrees BTC, and 25 degrees BTC.
We do not recommend this pulley be installed on "street-driven" cars that are used for stop-and-go driving. In addition, we do not recommend the use of this pulley on 1987-91 Turbo II engines unless modifications have been made (shorter intake runners, etc..) to increase the engine's RPM range substantially. Turbo II engines produce their peak power in a lower RPM range, relative to a non-turbo engine.
We do not recommend this pulley be installed on "street-driven" cars that are used for stop-and-go driving. In addition, we do not recommend the use of this pulley on 1987-91 Turbo II engines unless modifications have been made (shorter intake runners, etc..) to increase the engine's RPM range substantially. Turbo II engines produce their peak power in a lower RPM range, relative to a non-turbo engine.
02-03-11, 12:32 PM
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Hail Dented 7
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make sure you have the clutch pedal depressed the entire time by use of whatever device you prefer
Thanks all.
02-03-11, 12:40 PM
#5
Yikes, the whole front hub has to come off to install this thing. Besides risking dropping a bearing, that main bolt is usually a bitch to get out. There's a load of loctite on there from the factory.
Underdrive pulleys are not really meant for anything but race cars. Your weak S4 alternator is going to struggle to charge your battery at idle with this pulley.
Underdrive pulleys are not really meant for anything but race cars. Your weak S4 alternator is going to struggle to charge your battery at idle with this pulley.
02-03-11, 12:53 PM
#6
Use the starter bump method to break loose the bolt. It is an easy way to do a very hard thing. It's scary the first time you do it but later... well ok, it's still scary.
While you are in there, put an adkins thermal pellet in or shim the oil bypass valve. I did the shim method.
Good Luck.
Still do not worry too much. That bolt has a history of being a problem child. There was a long post earlier this year about that bolt and how to remove it.
The method I use was ragged on by the professional set that visits this site. I use a Craftsman half inch drive breakover with the 19mm socket. I rest the breakover on the frame of the car, left side. Get in the car and bump the starter. Nut comes loose. ON my car it does. Others say it does not work for them. Might take two or three tries. Make sure the socket is on good and the bar straight and up against the frame.
The method I use was ragged on by the professional set that visits this site. I use a Craftsman half inch drive breakover with the 19mm socket. I rest the breakover on the frame of the car, left side. Get in the car and bump the starter. Nut comes loose. ON my car it does. Others say it does not work for them. Might take two or three tries. Make sure the socket is on good and the bar straight and up against the frame.
02-03-11, 01:04 PM
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Hail Dented 7
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Use a 2x4 wedged into the front of the seat to keep the clutch down. Your wife doesn't have the patience.
Use the starter bump method to break loose the bolt. It is an easy way to do a very hard thing. It's scary the first time you do it but later... well ok, it's still scary.
While you are in there, put an adkins thermal pellet in or shim the oil bypass valve. I did the shim method.
Good Luck.
Use the starter bump method to break loose the bolt. It is an easy way to do a very hard thing. It's scary the first time you do it but later... well ok, it's still scary.
While you are in there, put an adkins thermal pellet in or shim the oil bypass valve. I did the shim method.
Good Luck.
I just read the directions on racingbeat, it does not mention the last part of your post. Is there a reason for this?
Last edited by VermontRX7; 02-03-11 at 01:06 PM.
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02-03-11, 01:07 PM
#8
She will be patient enough, sometimes we are just out there in the garage anyhow. and once shes on the pedal, ill tell her what it will cost if she lets off, and I know she won't LOL
I just read the directions on racingbeat, it does not mention the last part of your post. Is there a reason for this?
I just read the directions on racingbeat, it does not mention the last part of your post. Is there a reason for this?
02-04-11, 07:32 PM
#9
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I did this with the help of a friend and an impact gun. The friend had to hold down the clutch pedal for less than 10 minutes, and it's not like it's hard to hold down a clutch pedal.
I really don't know what the hullabaloo is about this part not being streetable. It strains a bit at night with all accessories going, but I really didn't notice it anywhere else.
As far as if you should bother? I dunno. It's really only useful if you are going to be wringing its neck quite often. It is part of a "system," and will need to be paired with an upgraded radiator to be effective at all (ask me how I know
)
I really don't know what the hullabaloo is about this part not being streetable. It strains a bit at night with all accessories going, but I really didn't notice it anywhere else.
As far as if you should bother? I dunno. It's really only useful if you are going to be wringing its neck quite often. It is part of a "system," and will need to be paired with an upgraded radiator to be effective at all (ask me how I know
)
02-04-11, 08:14 PM
#10
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Well inba street car, with a extremely weak alternator ( both s4 and s5) and a motor that does not like to be over heated, the point of an underdrive pulley makes little sense. You can pick up the same if not more of a power increase and better throttle response just by switching to a efan, which all said and done the only thing you can mess up is the radiator during the install, unlike the pulley. There is still a chance of the needle bearing dropping. Also if you have ac and ps those are going to be weaker aswell. I dont think the power gain and response (if any for the latter) is worth the inconvenience and extra strain being put on the acessories
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