SR20 Conversion Question

[wvitPR]

Hi,
I am fairly new to this forum, so forgive me if I am asking a question that has already been answered somewhere or maybe considered stupid, but it seems that SR20 engine swaps would be more popular if the frame of the roadster did not need to be modified.

So.... has there been any investigation into designing/building a custom sump for the SR20 that may give appropriate clearance to the x-member ? and a posible adaption of stock gearboxes to the SR20, I know it seems to be a massive task but how good would it be to have a complete conversion kit for the roadster ??

Comments on why the above would be phyically imposible would be appreciated, as I really have not had much expirence with the layout of the SR engines.

Many Thanks

[spriso]

Phil wrote:

has there been any investigation into designing/building a custom sump for the SR20 that may give appropriate clearance to the x-member ?

Hi Phil,

Your question is a good one and I will try to answer with experience that we gained when working on an SR20DE conversion into a Mazda Miata (MX-5).

The SR20DE(T) engine is a 'front sump' which means that the oil sump sits in front of the steering rack. The oil pan is configured of two parts, a cast aluminum upper pan, and a stamped sheet metal (steel) lower pan, like this:



Here is the basic layout of the upper SR20DE(T) oil pan:







The oil pan sticks forward about and inch which is partially what fouls the Roadster crossmember, but it is really the depth that is what interferes:





Looking at that last image, you could almost get away with not modifying the crossmember if you had a rear sump oil pan.... so, how do we get one of those? Let's go back to the Miata project...

The Miata uses a rack and pinion steering, and that works exceptionally well. Mazda goes to incredible lengths to get the steering feel right and if you have driven a Miata, you know how well it works. One of the things that you should never do when doing an engine swap in a Miata is move the steering rack, and we followed that rule!

The Miata uses a 'front steer' rack that is mounted in front of the crossmember, as opposed to the 'rear steer' rack in the Silvia (240SX) chassis. Our cast stock aluminum pan would have to go as it would not clear the steering rack.

Unfortunately, there are no rear sump oil pans for the SR20 engines-- you have to build your own. Putting one in a Miata is even more fun...

The SR is a much taller engine than the original Miata engine, so we had to mount the engine as low as possible in the chassis. We then came up with the absolute minimum thickness of oil pan possible that would still clear the steering rack but keep the engine as low as possible. What we did was make a side profile of the pan to figure out how short of a oil pan we could get away with. Here is a shot of us mocking up that demo pan:



The SR20 engine is an all-aluminum block, and the oil pan is a stressed part of the design. We needed our new rear sump oil pan to be as strong as possible, we did not want something that was made from 1/4" aluminum plate, especially since the SR20DE going into this car is an Autech version (200hp normally aspirated) which is hand built by Autech in Japan-- we were not going to find another one of these engines!

A custom oil pan was machined from a ~80 lbs. billet chunk of 6061 aluminum! A 6-quart oil sump was welded onto the bottom (in a rear sump configuration).













Overkill? Without a doubt! But we want this car to last, and have a bullet-proof oil pan setup (and we got it!) Credit machinist Jeff Klein for his outstanding work on this piece!

Here is car owner "Diamond Dave" with his SR20 powered Miata:



Just another of the projects here at Spriso Motorsports....

Michael

[wvitPR]

Hi Micheal,
Fantastic reply, thank you for your detail. So if using a sump with the same dimensions as your modified miata version, would the sr20 clear the x-member do you think ?, as maybe it might be possible to have a pattern made and get some sand casted ?, I have a few contacts over here and am looking for a project, and I feel building a pattern is in my scope of skills, what do you think?, maybe I am just a dreamer?

Best Regards, and thanks again for your effort so far.

Phil

[windy311]

It would be cheaper and easier to just cut it if your going SR20 route.
Rob

[spriso]

Phil wrote:

So if using a sump with the same dimensions as your modified miata version, would the sr20 clear the x-member do you think ?,

It is hard to say if I think it would clear-- it could be close for sure. I can tell you that building this rear-sump oil pan was a tremendous amount of work, and it was not cheap! The oil pan we built for the Miata project was a one off, we don't have any drawings for that application, but it would not be that difficult to replicate if you had a SR20 on an engine stand...

If I had a choice (in a roadster application), I would modify the frame rather than build a new oil pan. We have discussed this modification many, many times in great detail if you do a search.

My .02 yen, spend at will...

Michael