Project Endurance Miata: Trading a Turbo for a V6, but Do We Install a Honda J35 or a GM LFX?

The S-type and X-type 3.0s were both Duratecs. The S-Type and Lincoln LS were the 'same car'.  The big reason I know of why people tend to avoid the LS 5spd is because it's non-overdrive with 5th being 1:1.  Not that that matters on race car once you're swapping the rear end out for something in the low 3s:1 and you rev to 7000. For a street car it's more of an annoyance although realistically there aren't many engines you can swap into a Miata that will be any MORE pleasant buzzing 4000rpm going 70mph, so a gear swap is almost implied with any larger engine intended to make the miata a better street experience. 

Anwyay, I'm interested to see how this goes even though I personally (partially from my experience as a tech) am more interested in the Honda J series.  The LFX will still be fast as long as it's working, although you could say that about the turbo engine too.   All my fascination with the LFX sort of ended after driving Camaros and CTS's with the 6spd and still finding it meh. Taking off 1000+ lbs would help, but it was also about feel and nvh. Plus side is, for a racecar that practically doesn't matter at all! The LFX will be more powerful for a smaller amount of money (engine itself) than the J since only certain J parts are easy to make 300hp with and there is a market for them, versus the LFX in which 300hp versions are plentiful and enthusiasts more or less ignore them once they hit the junkyards. 

In reply to Vigo :

Non overdrive transmissions are great because they cut down on driveshaft RPM.  Which is not so much a "performance" benefit as it is  a benefit to not have to deal with a driveshaft spinning at 6000-7000 and your U joint angles are less than perfect and the oscillations wreck everything else in the drivetrain.

Ahem.

Knurled. said:

NickD said:

Too many years as a GM tech makes me nervous around LFXs.

Working on Hondas makes me interested in the J-series kit.

 

But the LFX kit should make for a much faster car.  The Hondas are not very acceleration prone, even in Accords.

 

I've heard that gripe too, that they are a little slow to rev. I wonder if a really light flywheel would make the J-series feel much sportier.

The main problems with the J swap that I've seen documented are the engine being cantilevered off a rear (bellhousing) mount, lack of ground clearance for the oil pan, and re-locating the steering rack.

If anyone out there is seriously tracking a Miata with the J swap, I haven't seen it on any of the various forums.

There was a guy up in brooksville florida that did the J swap, sounded like he was tracking it for a while and he showed up to one corvette autocross, but it seems he went to tracking bmws. Wish I took a good look at it when he did come, I saw it as "just another" miata at an autox with a different sounding motor

On a side note- questioning the V6 choice, seems like a good one to choose would be the one that has shown tons of success in cheap car endurance racing.

The Alfa v6.  

alfadriver said:

Keith Tanner said:

alfadriver said:

It's interesting that there isn't a Cyclone v6 swap out there being sold, too.  Last I saw, it was getting 300hp w/o DI.  Must be a much bigger engine....

For a different, and perhaps cheaper (but harder) option would be the Lincoln LS V6 with manual swap.  It's been done before, and drives really nicely- but not 300hp...

That’s the Jaguar V6 used in the Rocketeer kit, isn’t it? 

It’s a shame that GRM is doing a swap into a race car, because all the hard parts of a swap involve making it into a real street car. It’s the real way to test the R&D. 

I would recommend reinforcing the steering rack mounts in the V8R subframe and putting a cross brace between the rear control arm mounting points to avoid failures - especially on a track car. 

Dunno- I don't know what year of "Jag" engine they are using- if it's one from the early '00's, then it's really a Taurus engine- not an actual jaguar engine.  

And for anyone considering this swap in the US- the Lincoln V6 with a manual is a better choice, since it has a 5 speed transmission attached- just like the Camaro choice that GRM made.

Jaguar AJ30, which is the LS engine. Rocketeer mates it to the Miata trans, which means everything from the bellhousing back is Mazda engineered. Even the clutch is a Miata unit sourced from FM. It’s got a custom intake manifold with dual throttle bodies to fit under an unmodified hood, which I know was a problem with the one-off Lincoln car. Runs bespoke engine management.

In reply to Keith Tanner :

Dont forget, the Mazda 6 had the same family of V6 in it.

It's a more distant relative. That's the "Taurus" engine that Alfa referred to, I believe.

In reply to Keith Tanner :

To me, being able to to take most of the powertrain and swap the intake manifold is easier and more properly engineered than an adaptor plate set up.  but that's just me.

And that's why if you are in the US, find the LS V6 manual- they are still out there.

Keith Tanner said:

It's a more distant relative. That's the "Taurus" engine that Alfa referred to, I believe.

Uh, the Jag and Lincoln motors are both basically the Taurus engine.  The may have added a slightly different valvetrain, and did add electronic throttle.  But the engine is the basic Ford unit.

Jag people will cringe and argue that all day long, but it's the same engine.

Alas, this is too much of a tangent to the GM V6 being put into a cheap endurance car by GRM...  

alfadriver said:

In reply to Keith Tanner :

To me, being able to to take most of the powertrain and swap the intake manifold is easier and more properly engineered than an adaptor plate set up.  but that's just me.

And that's why if you are in the US, find the LS V6 manual- they are still out there.

Depends on where you think the difficult points are. If you use an LS transmission, you need to re-engineer either the Power Plant Frame or come up with a way to secure the differential and transmission. CMC had real trouble with the diff mount in their Locost design, the one that GRM built at the Mitty failed in about 20 miles. You also have to deal with where the shifter ends up. 

Meanwhile, a transmission adapter plate just has to be square and accurate. It's a flat piece of metal with two sets of holes. You'll also need a custom flywheel or a custom clutch, both of which are pretty straightforward.

I was led to believe that there was a bigger difference between the Taurus and the Jaguar/Lincoln engine from your previous comment, Alfa. Rocketeer used Jaguar because there are a lot of Jaguars in the UK, and an MOT-failed S-type is basically free. I'm not sure if they got the Taurus or the Lincoln. Mondeo would seem to be a common donor as well but the transverse mounting may bring some differences to it and there's a 15% horsepower difference if I'm reading Wikipedia correctly.

This is a long-running GRM project car, there will be lots of opportunities to talk about the LFX :)

Which is not so much a "performance" benefit as it is  a benefit to not have to deal with a driveshaft spinning at 6000-7000 and your U joint angles are less than perfect and the oscillations wreck everything else in the drivetrain.

Sounds like something you'd have to worry about if your differential and transmission weren't held in perfect alignment by a large C-channel.   In other news, i authored a whole thread about why i thought 3.63s in the stock housing was the best Miata mod for me as a 70-100 mph Texas street driver.  But again,  making a miata a better racecar is easier than making it a better streetcar. This LFX swap will still be a thrill ride in its intended environment.

Vigo said:

Which is not so much a "performance" benefit as it is  a benefit to not have to deal with a driveshaft spinning at 6000-7000 and your U joint angles are less than perfect and the oscillations wreck everything else in the drivetrain.

Sounds like something you'd have to worry about if your differential and transmission weren't held in perfect alignment by a large C-channel.   

Assuming you can get perfect alignment in the first place.  If there is a floor in the way, you might not.

This is, of course, a major advantage to keeping the Miata transmission.

Really makes me appreciate Guibos.  Or CV joints in the driveshaft.  

In reply to 759NRNG :

You are reading my mind.

The Honda option died when it reuired custome drivetrain bits to mate the engine to the gearbox. That never ends well and is a royal PITFA when servicing what broke. Refer to the OP where parts availbility at the nearest NAPA is a good thing.

In reply to NOHOME :

Oddly that is a point in the Honda setup's favor to me.  It uses junkyardable/FLAPSable everything except flywheel, and flywheels are generally not wear or failure items.  Meanwhile, when you swap transmissons, now you have a bunch of liability happening in the drivetrain if anything ever happens that damages the driveshaft.  And driveshafts are wear items, besides. And if the PPF gets eliminated, you're introducing chassis stress and NVH. Maybe not a big deal on a race car, but real important otherwise.

Rodan said:

The main problems with the J swap that I've seen documented are the engine being cantilevered off a rear (bellhousing) mount, lack of ground clearance for the oil pan, and re-locating the steering rack.

If anyone out there is seriously tracking a Miata with the J swap, I haven't seen it on any of the various forums.

Yeah, and the starter bottom center blows in my book. (Please correct me if this is no longer the case.)

wheelsmithy said:

Rodan said:

The main problems with the J swap that I've seen documented are the engine being cantilevered off a rear (bellhousing) mount, lack of ground clearance for the oil pan, and re-locating the steering rack.

If anyone out there is seriously tracking a Miata with the J swap, I haven't seen it on any of the various forums.

Yeah, and the starter bottom center blows in my book. (Please correct me if this is no longer the case.)

 

I wonder if adapting a rotary transmission would be easier.  The starter is on the trans side of the bellhousing like a Honda J application, and if you are bolting into a Miata, you use an '81-92 nonturbo transmission and stick the Miata tailhousing on it.

There are a lot of compromises with the J swap that you don't have with the LFX, but the LFX is basically an entire V6 Camaro with a Miata dropped on top. Which means it's in a different league as far as price goes. The article makes it seem like it's only a few thousand dollars difference, I think it's closer to $10k.

Thing 3 Racing out of Indianapolis has had success with their J swap in AER but I think you'd definitely need to go into it understanding the limitations. 

I wonder who the first person to Genesis coupe swap a Miata will be?

Knurled. said:

wheelsmithy said:

Rodan said:

The main problems with the J swap that I've seen documented are the engine being cantilevered off a rear (bellhousing) mount, lack of ground clearance for the oil pan, and re-locating the steering rack.

If anyone out there is seriously tracking a Miata with the J swap, I haven't seen it on any of the various forums.

Yeah, and the starter bottom center blows in my book. (Please correct me if this is no longer the case.)

 

I wonder if adapting a rotary transmission would be easier.  The starter is on the trans side of the bellhousing like a Honda J application, and if you are bolting into a Miata, you use an '81-92 nonturbo transmission and stick the Miata tailhousing on it.

The rx7 trans does not have a replaceable bell housing and the bolt pattern is different.  

Edit:  I realize you said adapting the rotary trans.  So adapter plate to rotary trans and then miata tailshaft so it still has ppf.

This solves the starter issue!

I still think finding a more suitable trans would make more sense.

sleepyhead the buffalo said:

I wonder who the first person to Genesis coupe swap a Miata will be?

I wonder who the first person to LFX swap a Genesis will be? They've already been LS-swapped for Formula Drift use, but the chassis proved to be pretty unsatisfactory, as every driver who tried one dumped it in pretty short order.

wvumtnbkr said:

Knurled. said:

wheelsmithy said:

Rodan said:

The main problems with the J swap that I've seen documented are the engine being cantilevered off a rear (bellhousing) mount, lack of ground clearance for the oil pan, and re-locating the steering rack.

If anyone out there is seriously tracking a Miata with the J swap, I haven't seen it on any of the various forums.

Yeah, and the starter bottom center blows in my book. (Please correct me if this is no longer the case.)

 

I wonder if adapting a rotary transmission would be easier.  The starter is on the trans side of the bellhousing like a Honda J application, and if you are bolting into a Miata, you use an '81-92 nonturbo transmission and stick the Miata tailhousing on it.

The rx7 trans does not have a replaceable bell housing and the bolt pattern is different.  

Edit:  I realize you said adapting the rotary trans.  So adapter plate to rotary trans and then miata tailshaft so it still has ppf.

 

This solves the starter issue!

 

I still think finding a more suitable trans would make more sense.

Especially since you're specifying a transmission that is between 39 and 28 years old.

In reply to Keith Tanner :

NC 5 speeds are the same trans, too.

Excellent choice,, doing one myself!!