Transverse mounted fwd engine motor mounts
Transverse mounted fwd engine motor mounts
(OP)
I'm new here so stop me if I'm asking an obscene question.
I hear all the time how guys in a front engine rear drive setup are relocated or modifying the motor mounts to put the engine a few inches further rearward in the engine bay. This is mainly done to improve front/rear weight distribution. My question to you, oh knowledgeable ones, is:
What kind of problems will I face designing new engine/trans mounts to move a transversely mounted fwd engine 3-5 inches rearward. This car will see both drag strip and autocross and is a general street fun car. For drag racing, moving this particular setup rearward would actually concentrate the weight of the drivetrain over the front tires, improving traction. For autocross, this will greatly improve the 65/35 f/r weight distribution; with a 2300lb car and the engine and transmission combo weighing right around 400lb, that's a nice chunk of mass.
The few problems I can think of would be:
Halfshaft angle: Obviously, putting the transmission 3-5 inches further rearward will increase the halfshaft angle between the trans and the front hubs. How will this affect performance and wear?
Shift linkage: This car uses two bars, one being a shift rod and the other being a stabilizer. Being a hollow tube with relatively generic ends, remaking these slightly shorter shouldn't be too much of a problem.
Thank you for your time and I appreciate any opinions/ideas you may have to offer. I look forward to your replies.
Eric Mills
I hear all the time how guys in a front engine rear drive setup are relocated or modifying the motor mounts to put the engine a few inches further rearward in the engine bay. This is mainly done to improve front/rear weight distribution. My question to you, oh knowledgeable ones, is:
What kind of problems will I face designing new engine/trans mounts to move a transversely mounted fwd engine 3-5 inches rearward. This car will see both drag strip and autocross and is a general street fun car. For drag racing, moving this particular setup rearward would actually concentrate the weight of the drivetrain over the front tires, improving traction. For autocross, this will greatly improve the 65/35 f/r weight distribution; with a 2300lb car and the engine and transmission combo weighing right around 400lb, that's a nice chunk of mass.
The few problems I can think of would be:
Halfshaft angle: Obviously, putting the transmission 3-5 inches further rearward will increase the halfshaft angle between the trans and the front hubs. How will this affect performance and wear?
Shift linkage: This car uses two bars, one being a shift rod and the other being a stabilizer. Being a hollow tube with relatively generic ends, remaking these slightly shorter shouldn't be too much of a problem.
Thank you for your time and I appreciate any opinions/ideas you may have to offer. I look forward to your replies.
Eric Mills





RE: Transverse mounted fwd engine motor mounts
If this powertrain relocation involves rotating it in any way as seen in side view, there will be fluid level consequences both in the engine sump (including the pickup) and in the transaxle (especially if automatic). Further, and particularly if it's a V-type engine, oil drainback from the valve/cam cover volume(s) may not be as good under certain conditions.
Norm
RE: Transverse mounted fwd engine motor mounts
As far as drag racing, moving the weight backwards to over the front wheels will only decrease traction up front. All other things remaining the same, it will only increase weight transfer to the rear.
Those are pretty short half shafts, so you will be adding substantially to the basic angles of the CV joints. It might live if your engine is still basically stock and all you do is race ocassionally. If you have added power or plan on many street miles it will simply wear them out or break. Once you figure out what the new angle will be on the outer CV's, as viewed from above, you can immediately subtract it from your available steering angle in each direction. Don't forget to readjust the stops!
You may soon find you car is no longer so "fun".
RE: Transverse mounted fwd engine motor mounts
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Transverse mounted fwd engine motor mounts
Ummm, less traction = less acceleration = less rearward load transfer (still assuming the same CG height). The "new" vertical rear wheel loading under acceleration will be greater than the "old", if that's what you had in mind.
Norm
RE: Transverse mounted fwd engine motor mounts
Sidenote: I did plan on designing these mounts to lower the engine a couple inches. I only say a couple because the car itself is barely streetable up here on the wonderful roads of Michigan as it is.
Eric Mills
RE: Transverse mounted fwd engine motor mounts
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Transverse mounted fwd engine motor mounts
Some things might actually tend to favor both auto-x and drag in a FWD car, such as a slightly smaller rear wheel/tire package that that used up front. Not as small as a dedicated dragstrip car, but perhaps 20mm narrower. A 2200 lb car with less than 40% rear weight may not heat up competitive tires (in let's say 225mm section) soon enough to be useful over much of the run, and the understeer/oversteer balance will shift as the fronts do. Especially on cooler days. Some folks are already experimenting with 205's on the rear only in a class that permits 225.
Depending on whether you're a follower of the so-called "soft spring/big bar" approach to suspension tuning or oriented more toward using the bars more for fine tuning probably has greater influence on how you decide to handle that will than a couple or three percentage points of weight distribution will (obviously I haven't run any numbers here). So might the difference between being a "point and shoot" driver or one who more smoothly carries momentum through the course elements. There is even some disagreement among FWD auto-x'ers regarding front vs rear spring rates and getting the car to rotate. Anyway, my initial thoughts in light of your comment about "a couple of inches lower engine placement" (or complete sprung mass lowering) is generally that the stiff spring/light bar(s) plan may be preferable, with ride comfort essentially being ignored.
Norm
RE: Transverse mounted fwd engine motor mounts
If it brought any advantage in drag racing, and I can't see that it would, it might be worthwhile, but it will absolutely kill the car for autocross. You might as well drive a bus.
Mike Halloran
Pembroke Pines, FL, USA
RE: Transverse mounted fwd engine motor mounts
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Transverse mounted fwd engine motor mounts
As well as not specifying the class of X cross racing, he does not specify location, so unknown local rules might apply.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Transverse mounted fwd engine motor mounts
This car is really more of a street car/fun weekend car than a dedicated track car. I would venture to say the time in this car is 60% street, 25% drag, and 15% autox.
Eric Mills
RE: Transverse mounted fwd engine motor mounts
This is just my opinion, but dealing with this car and it's intended use...Unless you have some masochistic leaning that your not telling us...I would consult with some of the purveyors of Ford mod parts, Bat (British American Transfer) Ent., Esslinger Engineering, etc.(probably many more that I am not up on), to get a feel of what you can do to improve the performance of your car within the accepted norm...Again, JMO, there is enough things you can do to alter the performance of a FWD car as to 'boggle the mind'...without all the hassel you suggest.
An Escort is not my first choice to through money at, but, 'what ever trips your trigger'. I worked over a Fiesta once and folks thought I was nuts, too...so enjoy.
Merry Christmas
Rod
RE: Transverse mounted fwd engine motor mounts
You'd probably need outboard bearings on the diff output shafts to deal with the belt tension.
Mike Halloran
Pembroke Pines, FL, USA
RE: Transverse mounted fwd engine motor mounts
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Transverse mounted fwd engine motor mounts
The topic at hand is for my other zx2. I use these cars because they're not generic. I have muscle and import guys alike coming up to me at the drag strip applauding my efforts. It's a passion for me and I'm always looking for something else to modify/fabricate.
Mr. Halloran,
I see where you're coming from but I'm trying to steer clear of additional complexity and packaging would mostly likely be a prominent issue in your idea, as this is quite a small car.
Eric Mills
RE: Transverse mounted fwd engine motor mounts
Turn the seat 180 degrees.
Lock the front wheel steering straight ahead.
Move Steering wheel, pedals dash etc to the rear, facing the driver as he faces the rear.
Install rear wheel steering that operates via the steering wheel and disconect steering wheel from front wheels.
Flip the Crown wheel over so that gear box output is reversed in direction of rotation.
Weight transfer now becomes your friend instead of your enemy.
Don't drive at night as the head lights are really bad and the reversing lights are blinding to following traffic.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Transverse mounted fwd engine motor mounts
You know the Mini is my first effort (absent the abortive Fiesta) at racing a FWD. It's---well---different! It's taken me five years to get down to class record times and feel confident in my ability (such as it is, these days) to compete (at least 'keep up') with the younger crowd. So, don't give up so easily. Having watched a couple of the Speed Channel shows on FWD drag cars...I'm amazed. These guys are turning times that would have smoked a AAF car of my drag days!
Rod