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mounting engine low. driveshaft angle?

Old 03-26-08, 03:12 AM
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mounting engine low. driveshaft angle?

Hey guys, I was searching through some old buildups and saw some really nice dry sump oiling systems, so they mounted the engine really low. I was wondering about the driveshaft angle though.
Do they have the tranny tilting upward slightly? But then the front of the engine would slighlty being pointing downward.
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Old 03-26-08, 07:20 AM
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You just need to make sure the pinion angle is parallel to the output shaft. So, if the tranny is pointing up 2 degrees, the pinion should be pointing down 2 degrees.
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Old 03-26-08, 07:40 AM
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There is a maximum driveshaft angle...

But I wouldn't worry about it unless you're serious about going dry sump...
The Mazda Comp "kit" was over a grand.
And you still need the oil pump / lines / reservior!
The oil reservior is not easy to fit under the hood...


-Ted
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Old 03-26-08, 12:19 PM
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In a full on race car it's usually in the cabin somewhere.

One note on dropping the engine, most/all racing classes won't allow for the engine to be moved at all, so if you're doing this for racing, be sure to check the rules.
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Old 03-26-08, 01:19 PM
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Originally Posted by jgrewe View Post
You just need to make sure the pinion angle is parallel to the output shaft. So, if the tranny is pointing up 2 degrees, the pinion should be pointing down 2 degrees.
So do people just add spacers to have the nose of the diff pointing downwards a little?

I brought this up just for disscussion. I dont have the money nor plan on mounting my engine lower. I saw the pic of a guys 20b with dry sump and saw how rediculously low he could mount the engine. I was just wondering how the U joints in the driveshaft could handle that sort of angle
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Old 03-26-08, 06:08 PM
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It shouldn't just be parallel, but in line. Basically you don't want the u-joints to have to rotate much if any.
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Old 03-26-08, 06:40 PM
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Do they add spacers and try to get the it all in line? Lowering the diff is a possibility, but then the axle angle and the ground clearance gets screwed up.
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Old 03-26-08, 07:07 PM
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Originally Posted by Black91n/a View Post
It shouldn't just be parallel, but in line. Basically you don't want the u-joints to have to rotate much if any.
? I think ive read differently,

I believe ive read that you want both ends of the drive shaft parralel like someone previously posted but not in a straight line, because it will vibrate
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Old 03-26-08, 09:44 PM
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Originally Posted by Black91n/a View Post
It shouldn't just be parallel, but in line. Basically you don't want the u-joints to have to rotate much if any.
You slipped up there, Black91n/a. I think that is the first time I've ever seen something incorrect come from you. I'll have to mark my calender so when you catch me screwing up I can bring up this day in March 08

You want to make the u-joints to work a little. 5 degrees is about the max you would ever want. It sounds crazy but it will cost you HP and then u-joints when they wear out quickly.

You can usually just lower the whole engine/ tranny the same amount and keep things in phase.
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Old 03-26-08, 11:20 PM
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Well I wasn't meaning getting out a lazer alignment kit or something like that, but the point is that you don't want large amounts of misalignment, which could happen even with parallel input and outputs.
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Old 03-27-08, 04:24 AM
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Where do I buy this lazer alignment kit? LOL

5 degrees is not much. I was looking at this awesome picture when I thought of this question https://www.rx7club.com/attachment.p...5&d=1154734239

It must have like a 15 degree angle if you didnt do anything to get the angle right. Maybe more. Also being able to mount it further back also. The length from tail of tranny to driveshaft isnt much, which means more angle. What are some ways people have been correcting the angle? Are there ways besides major fabrication?
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Old 03-27-08, 08:16 AM
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I just use my digital Smartlevel and put it on the flange of the rear end and the bottom of the engine. Those are the two flat surfaces that I've found to be easiest. You just make sure you are the same number of degrees from horiz/vert in the right direction. (if tranny is pointing down the diff should point up, there are other ways to set it up but this is the most goof proof)

Usually some spacers on the tranny mount is easiest but any place you can change the height of will work.

You can run a bunch of angle but it will cost you HP. Here is another curve ball for you, if you have rubber bushing in the rear you need to account for how much the rear is going to twist when you are on the gas. I'd start with about 1- 1 1/2 degree difference. This is more of an issue on live axle cars than on an FC.
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Old 03-27-08, 12:47 PM
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Originally Posted by initial D is REAL! View Post
Where do I buy this lazer alignment kit? LOL
When setting up pumps in an industrial setting, alignment of the motor and pump shafts is critical, and they use lazer alignment tools there.
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Old 04-11-08, 10:41 AM
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I disagree with you also black91. . . also much to my surprise.

One should intentionally NOT have a straight line from crank, or in this case eccentric, through the tranny, through the driveline, through the pinion. One does want the tail of the tranny and the nose of the diff parallel, but NOT on the same line.

http://www.carcraft.com/howto/91758/index.html
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Old 04-11-08, 11:13 PM
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I gotta question how applicable that Car Craft link is to our FC / FD IRS?
It sounds like all live axles set-up's - I only see mention of 4-link and leaf type rear suspensions.
I don't think most of our IRS' rotate and move as much as a live axle.
In fact, the vertical movement in an IRS is almost nil.

The article does state that the best position of the drivetrain is "straight"...under load.


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Old 04-12-08, 04:04 AM
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Very good point. Black91n/a and RETed know their stuff. The angle a U joint takes is not very much.
QUOTE=CrackHeadMel;8023534]? I think ive read differently,

I believe ive read that you want both ends of the drive shaft parralel like someone previously posted but not in a straight line, because it will vibrate[/QUOTE]

i'm curious though haveing the driveshaft perfectly straight is bad?
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Old 04-12-08, 05:10 AM
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I dunno why anyone would say that also...

The U-joints are "strongest" when everything is straight.
The Car Craft article even states that you get minimum loss of power when the U-joints are straight.
You can easily test this yourself with a ratchet / socket U-joint...
See how much harder it is to turn when the U-joint is off-angle?

Ideally, if you could keep the transmission (tail shaft) and rear diff from moving, then you could run a straight driveshaft with NO U-joints...ideally.

The Car Craft article mentions differing angles due to "preload".
Once load is induced through the drivetrain, the U-joints are then straighten out.


-Ted
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Old 04-12-08, 02:23 PM
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OK good, I'm not crazy. I thought straighter angle is better
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