Have seen lots of builds of NA 20b's and 26b's where they lower the engine ~2 inches and move it backwards 5+ inches with a shorter driveshaft for better weight balance. My question is, has anyone ever done this with a regular 13b twin or single turbo? Is it possible?

 

Just about anything is possible when you throw enough money and time at it. I have not seen anyone do it on an FD with the stock engine and transmission though. Given the stock weight balance is already quite good, there would be little benefit to this exercise.

 

^Exactly. And even if it wasn’t already very good, unless you’re VERY experienced track junky, you wouldn’t capitalize on any balance improvement anyway.

 

Hard disagree.. lowering the engine is one of the best things you can do for both performance and driving feel.. anyway I guess no one has done it so I'll be the first

 

So apparently this IS for a street driven car. And you intend to lower and move the drive-train rearward on a relatively low-slung car from the factory that already has near perfect balance F-R. There’s a reason you’ll be the first.

 

The FD already has the entire 190lb (shortblocks) engine behind the front wheel centerline. This gives the car an extremely low polar moment of inertia, low cg, and great weight distribution.

A dry sump would allow you to lower the engine a few inches but you will need to modify your subframe.

Relocating the battery to the rear bin or trunk and swapping out the engine irons for billet aluminum would be much easier than a dry sump, let alone cutting the firewall and trans tunnel to move a 13B rearward.

Iron 20Bs are heavier and hurt the PMI and weight distribution of the FD, plus there are steering rack geometry compromises that make moving those engines rearward worth the extensive effort. It's not needed or worth it for a 13B unless you're trying to achieve something specific.

 

I think if you research weight and balance calculations for small aircraft, you'll find what you're looking to achieve will net virtually zero. As mentioned, the powerplant is centralized already and does not weigh much. The actual effect on driving dynamics of the car it has is about as optimized as it can be. Mazda had it right.

It's all about balance. moving the engine back, moves the transmission back and deletes the ppf and shortens the driveshaft. It would force both intake manifolds to be custom made as well. The wieght distribution forward of the firewall would be grossly imbalanced with the rear of the car. You would end up with a front that is TOO LIGHT and the car would absolutely drive awful. Dont even need it to exist to know that. Finally, the rigging of getting the motor mounts sorted out would be nonsense.

Theres no reason to do this and you will ruin an fd in an attempt that you will ultimately abandon if you initiate it.

For the amount of effort you would put forth, you could learn a new language instead. It would be a better use of your time.

 

Lightening the front of the car would not make it awful to drive, and it would actually provide more performance potential with the right supporting adjustments/modifications. It's actually better from a handling/grip/and performance standpoint to have more weight on the rear than the front. For an FD, this would typically require more front roll stiffness (stiffer front swaybar), and wider rear tires.

I think the main takeaway of this conversation is that there are far easier ways to lighten the front of the FD than to move the engine, and that there is not a major reason to do so (or problem to solve) with a 13B vs a nose-heavy car with a cast iron straight-6 like a Supra or GTR.

 

Moving the 13B-REW and transmission down and back would improve FD dynamics, but it requires a LOT of work and money.

The RX-8 already moved the engine down and back from the factory as well as moved the gas tanks forward ahead of the rear axle for lower polar moment of inertia.

It would be easier to start with the superior RX-8 chassis and 13B-REW swap it.

If you really need to do it in an FD, the RX-8 transmission is ~2" shorter to the shifter, so you can use that to help bring the engine back.
Will have to modify front subframe or use the Defined 20B subframe to get the engine on top of rear part of subframe and move the engine mounts back.

Will need a factory drysump front cover/system to get the engine lower.

Will need to fabricate revised power plant frame or eliminate with mounts like a V8 swap.

Shorten downpipe.

Before you do all that, please work with a fuel cell company to make a rear seat fuel cell like they do for Porsches. I want to do that for my car, it would be great if there was one already designed.

 

Too light in the front and you may raise the issue of the inside front tire lifting off the ground in hard cornering and acceleration - that means you can get understeer (too little load to develop grip) or oversteer that is VERY hard to eliminate. We have that issue in light formula cars, so you may not have that issue as long as you're on street tires, not some super-grippy slicks.

Front wheel drive cars sometimes have the lifting issue in the rear, especially during braking..

 

Reduce your front roll stiffness, increase the rear, increase rear spring rate, raise rear roll center, lower front roll center.... There's a lot of things to address an issue of reduced front grip and lifting an inside front tire on throttle. Generally speaking those would be good problems to have in an FD based off how most of them handle.

 

I mentioned the inside front lifting as a possibility with a very light front weight distribution. All the things one can do to reduce inside front lifting also increase oversteer unless you go to much wider rear tires, etc., and that's another can of worms. So F-R weight distribution is something to be aware of.

 

The other thing that can happen with front inside lifting is that the front CG gets higher, and the higher it gets, the more it overloads the outside rear, resulting in incurable oversteer. Making the rear stiffer reduced the lifting but didn't help with the oversteer. I once had a car (Formula Ford) given to me to drive in an invitational event that had that issue because the car's CG was way too close to the rear. It killed rear tires after a couple of laps and was a PITA to drive.

 

Your statement that "reducing understeer is VERY hard to eliminate" isn't that difficult and I have multiple options. Reducing understeer is increasing front grip and/or reducing rear grip. Every setup option has varying levels of compromises, but does not always inherently (or should not) "increase oversteer" -if tackling the issue properly. Car setup is always a compromise and a spiderweb of connected dynamics where one adjustment affects many others. The key is to make the best adjustment with minimal negative side effects while addressing the biggest issue the more effective way possible.

Dynamic Cg can increase when the front tire lifts. This does not inherently "overload" the rear tire and often increases rear grip (which you have stated in your comments of inside lift creates understeer that is VERY hard to eliminate".). The effects of weight transfer changes when changing weight distribution will vary from car to car and is often relative to the setup of a given car.

It's difficult to generalize tire wear and handling characteristics on one car and apply the resulting effects of a given change to a different platform.

0.02

 

So many braindead replies it's not even funny...

 

Then move along.

You've got the replies of multiple actual racers and experienced track divers with decades experience with these cars. What you're looking to do is doable, with enough money, but fairly pointless. If you know better, go for it, and stop waiting for validation.

 

It's been done, a fair way from a production FD however! Front and rear structure, floor and firewall cut out, rear of engine ended up around mid calf, a marginal DGB(?) out back, a ~ 300mm torque tube linking both, dry sumped. Fuel and oil tanks ended up where bins or rear seats would be if the rear cabin was intact. From memory, installed a 20b - and promptly went into a wall about 20 years ago.

 

I'm not waiting for validation, just checking if anyone else has done a particular modification, one which is the standard practice on all NA race builds, including 2 rotor builds, and is in fact a very useful modification for well established reasons.

The question was simply whether anyone has done said modification on a turbo build. If you have any useful contribution to make about the challenges involved with this, then by all means please let us know.

On the other hand, if you just came here to tell us your opinion that lowering COG/roll is 'pointless', maybe take your autism somewhere else.

Telling people to move along from their own thread is some crazy work bud! 👏

 

no, its too much work. the only reason people do it with the 3 and 4 rotors is because they have to.
Super Now! does make some -10mm engine mounts, but they are meant to be used with the engine stiffener plate, which is 10mm

remember the FD starts with a good weight distribution, and you can relocate some easy stuff (battery...) and make it better

 

Interesting about the super now mounts, but -10mm isn't much, -50mm or more would be the dream

For the record, all the 'low hanging fruit' mods (battery etc) are already being done, hence looking at more custom fab work

 

I'd argue that you're being the autist in this scenario. It's be acknowledged by multiple that it's a good thing - though also the issue of HOW good of a thing given the amount of work it would take has also been brought up. Go do you, be a unicorn and start shitting rainbows on all us plebs.

 

Maybe take your attitude somewhere else

You being an arrogant clownshoe to community members who have real world decades with this chassis experience versus your unfounded confidence with lack of experience "I know better" with nothing real to show for it attitude ("guess I'll be the first" no you won't and no one cares) is the real crazy work here "bud" 👏

 

Out of your 11 posts on this forum, you call people 'brain dead' in your 9th post and continue insult people after they answered your question. Not a great start.

To directly answer your question: Of course it's possible (to lower a turbo 13B).

Basic logic would dictate that if an NA13B could be lowered, so too would it be possible to lower a turbo 13B since the major challenges in doing so are the same whether NA or FI, and the fitment of the extraneous turbo components is very easy by comparison. Lowering and fitting 20B & 26B engines is SIGNIFICANTLY more difficult than a 13B.


You continue to post the same questions when multiple people have answered them.

1) If you want to lower the engine 50mm, you will need a dry sump oiling system (and figure out where to mount the oil tank) and modify or fab a new front subframe. You will need to move the engine rearward slightly to clear the power steering rack, but many people screw up the steering geometry by mounting the rack further forward.

2) If you want to move the engine rearward (more than an inch or so depending on the intake manifold and transmission), you will need to cut out and clearance the firewall and possibly the transmission tunnel depending on how far rearward you want to go.

...these are all pretty basic/obvious.


What challenge are you actually trying to overcome? Do you want to improve some fundamentals for the sake of improving fundamentals? Based off of your questions and comments, I would guess that you would have a challenge setting up your car to make it handle and extract the benefits these changes. I will restate my original advice that the time/money is better spent on replacing the irons with billet aluminum vs going down this path (on a 13B).

Are you racing your car and would the series you compete in even allow these modifications?

Are you a fabricator? I have the suspicion you are not because you would see the dimensional limitations of the chassis and would just do these modifications on your own and not ask the internet for advice.

.

 

Only your’s. Including those in your other threads asking how much boost you can put to the engine, cavalier replies about making “500 whp” and now this.
But you are correct that it’s not funny.

 

So you are already running drop hubs right? Because you would have to be brain dead not to do that first lower the mass of the of the entire chassis and driveline while retaining factory geometry?