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Login to post Forums » Grassroots Motorsports » Pardon me, but would you mind imparting some E30/Spitfire wisdom on me?

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Feb. 2, 2011 4:23 p.m. Tom Suddard SonDork

Ok, without giving too much away, I need a little help. I know you folks are the engineering type, so if you could I need a few answers to the following questions (keep in mind my total budget is $2011).

What do you know about turboing M20s (E30 2.5 liter)? I think we've discussed it before, but I need a refresher. How much boost can they take, how easy are they to megasquirt, what turbo should be used, etc.

How does an M20 compare to a GT6 engine in terms of size and weight?

How much power can a stock Spitfire rear differential take?

How wide is an E30 rear subframe?

How wide is the rear track of a Spitfire?

How far apart are the front framerails on a Spitfire?

What's the cheapest way to convert the front of a spitfire to a 4x100 bolt pattern?

What cheap, narrow, double wishbone front suspensions are out there? Miata, Civic, ?

Thanks, looking forward to any answers you can provide.
Feb. 2, 2011 4:41 p.m. WilberM3 HalfDork

e30 rear subframe is about 51" total width, just a hair over 48" hole-to-hole.
Feb. 2, 2011 5:16 p.m. Ian F SuperDork

All I can add is for M20 turbo and MS info, r3vlimited and e30tech are probably the best sources.
Feb. 2, 2011 5:29 p.m. mad_machine SuperDork

I think I would be more tempted by s52 into a Spit/gt6 and forgo all the turbocharging
Feb. 2, 2011 5:32 p.m. Ian F SuperDork

<-- now has mental picture of an S52 valve cover sticking out of a Spitfire bonnet... Hot Wheels style...
Feb. 2, 2011 5:32 p.m. unevolved HalfDork

Send me an email with whatever measurements you need, and I'll try to get some for you this weekend.
Feb. 2, 2011 5:35 p.m. Tom Suddard SonDork

You don't need to do that, but thanks.

No $$$ for an S52, if I could afford that then it would be going in my BMW, not in a Spitfire. I'm just looking to go faster than the Ro-Spit. Should be easy, right?
Feb. 2, 2011 6:25 p.m. stuart in mn SuperDork

Lots of guys have been running 15psi of boost on their M20 engines. There's a guy on the mye28 board who goes by the screen name of Turbodan who built up a e28 528e to the point where it's crazy fast; I think his engine is up to 18 or 20 psi. I don't condone street racing, but here's a video of him walking away from an e90 335i: http://www.youtube.com/watch?v=vfPxczTk6ag
Feb. 2, 2011 6:35 p.m. Ian F SuperDork

Tom Suddard wrote: How much power can a stock Spitfire rear differential take?

It seems a couple of hundred or so is about the limit. Judging by a few of the 3.5L V8 conversions I've seen. But I'm not sure those cars would see some of the abuse that a Challenge car would see.

What's the cheapest way to convert the front of a spitfire to a 4x100 bolt pattern?

I'd love to know this as well... since PRI's conversion hubs are by no means cheap. There's a guy on r3v who sells custom adapters, so that may be an option.

One of the NASS guys was playing with using Miata up-rights on a Spitfire, but I haven't heard him mention anything about it in a couple of years.
Feb. 2, 2011 6:47 p.m. MadScientistMatt Dork

Tom Suddard wrote:

Ok, without giving too much away, I need a little help. I know you folks are the engineering type, so if you could I need a few answers to the following questions (keep in mind my total budget is $2011).

What do you know about turboing M20s (E30 2.5 liter)? I think we've discussed it before, but I need a refresher. How much boost can they take, how easy are they to megasquirt, what turbo should be used, etc.

They take to boost pretty well. Seems a lot of the budget builds use Holset HX35's off diesel trucks.

MegaSquirt is a pretty well documented install on these (I need to come up with an official write-up for the DIYAutoTune.com site one of these days for the regular MS - already got one for the DIYPNP.) The biggest tip if you haven't seen it - put a 10K to 20K resistor inline with the crankshaft position sensor for accurate triggering at high RPM. Also, if you're putting an eta bottom end on it, be sure you get the regular non-eta crank trigger. Etas used a flywheel triggering setup that is a bit of a challenge to get it to work with (the ECU had a dedicated circuit that counted teeth on the flywheel ring gear).

How does an M20 compare to a GT6 engine in terms of size and weight?

M20s are surprisingly light - these guys say it's 258 lbs. Not much heavier than a Spitfire four banger.

How much power can a stock Spitfire rear differential take?

Not sure, but breaking the U-joints scares me even more than the diff.

How wide is the rear track of a Spitfire?

48" on earlier ones, 50" on the later Spitfire 1500. Front is 49".

What cheap, narrow, double wishbone front suspensions are out there? Miata, Civic, ?

Not much as narrow as 49", though if you cut up and welded the K-member that might not matter so much. Mini-trucks may be possible donors; the Chevy S10s and most of your Japanese trucks have double wishbones.
Feb. 2, 2011 6:51 p.m. Stealthtercel Reader

Tom, is there any way you can parlay all this into an International Baccalaureate credit, or will it just be a(nother) fascinating line on your CV?
Feb. 2, 2011 6:52 p.m. kreb Dork

Matt said: M20s are surprisingly light - these guys say it's 258 lbs. Not much heavier than a Spitfire four banger.
I think that you should avoid hanging out with crackheads. 258 lbs? Maybie for the long block.
Feb. 2, 2011 7:04 p.m. njansenv HalfDork

300whp is easy on the stock bottom end: they say upgrading the headbolts isn't a bad idea. Some have pushed 400+whp on stock bottom ends, reasonably well tuned. E30tech seems to be a better source for boosted stuff, or it used to be. R3v seemed better for M/S50 swaps.

I don't think making power will be your problem: the rear-end and u-joints might be. It sounds like a really cool project!
Feb. 2, 2011 7:04 p.m. Tom Suddard SonDork

Stealthtercel wrote:

Tom, is there any way you can parlay all this into an International Baccalaureate credit, or will it just be a(nother) fascinating line on your CV?

I'm not sure, but you can tie almost anything into your CAS hours (community service hours). I'm sure going to try.

At this rate, by the time I turn 18 my CV is going to be so long I'll need to bind it into a book...
Feb. 2, 2011 7:08 p.m. Tom Suddard SonDork

njansenv wrote:

300whp is easy on the stock bottom end: they say upgrading the headbolts isn't a bad idea. Some have pushed 400+whp on stock bottom ends, reasonably well tuned. E30tech seems to be a better source for boosted stuff, or it used to be. R3v seemed better for M/S50 swaps.

I don't think making power will be your problem: the rear-end and u-joints might be. It sounds like a really cool project!

Yeah, that's what I was concerned about, and where the idea to use the entire E30 rear subframe came from.

My dad made 225 hp and 200 ft-lbs. of torque with his Ro-Spit. It weighed 1650 pounds. My one and only goal with this project is make at least 226 hp, 201 ft-lbs. of torque, and have it handle decently. Getting the weight to 1649 pounds wouldn't hurt my feelings, either.

Seeing the looks on my friends faces when I open the hood in the high school parking lot will be nice, too... I'm planning on keeping it fairly subtle, and I'll run stock spit wheels on the street.
Feb. 2, 2011 7:34 p.m. MrJoshua SuperDork

Cut the pan off of a miata, shorten it a few inches, and stick a spitfire body on it. At that point you might as well run a boosted Miata motor in there. Your power goals are easy to attain with that setup.
Feb. 2, 2011 7:36 p.m. kreb Dork

Look here: http://www.r3vlimited.com/board/showthread.php?t=99913

m20 dressed = 180 kg = 396 lbs.

m52 = 150 kg = 331 lbs.
Feb. 2, 2011 7:48 p.m. mad_machine SuperDork

why not an SR20 turbo swap?
Feb. 2, 2011 7:54 p.m. Wayslow Reader

I have a 1973 Spitfire and a Europa. I changed the bolt pattern to 4 x 100. I'm going from memory here but I think the original lugs had a 0.48 knurl so I picked up some 1/2-20 lugs with a 0.65 knurl. The original bolt pattern is 3.75 or 95.25mm on centre so you need to move the centres over about 2mm. You need a milling machine to do this since a drill press will never hold a bit straight enough. The first hub took a couple of hours but the rest went quicker. BTW Miata Daisies look cool without the centre cap
Feb. 2, 2011 8:02 p.m. Tom Suddard SonDork

This idea was really a result of what I have , what I already know a lot about, and what's cheap. I already have a pile of M20 parts. Also, if I have two cars with exactly the same engine, life will be simpler.

Also, there's a strong possibility a free S14 (E30 M3 engine) will be coming my way in a few days/weeks/months/years. Fair market value makes it unusable for the challenge, but it's a good incentive to set the car up for a BMW engine.

Once I get the car up and running with an M20 (which I know like the back of my hand) swapping to almost any other BMW engine will be easy. I'm thinking I'll do the challenge with a cheap M20, then further down the road I can spend lots of money putting something more interesting in it.

I'm also looking for a test mule to learn turbocharging on, because I don't want to blow up my daily driver.
Feb. 2, 2011 8:03 p.m. Tom Suddard SonDork

Wayslow wrote:

I have a 1973 Spitfire and a Europa. I changed the bolt pattern to 4 x 100. I'm going from memory here but I think the original lugs had a 0.48 knurl so I picked up some 1/2-20 lugs with a 0.65 knurl. The original bolt pattern is 3.75 or 95.25mm on centre so you need to move the centres over about 2mm. You need a milling machine to do this since a drill press will never hold a bit straight enough. The first hub took a couple of hours but the rest went quicker. BTW Miata Daisies look cool without the centre cap

I've got a mill and I know how to use it...
Feb. 2, 2011 8:28 p.m. Wayslow Reader

Tom Suddard wrote:

Wayslow wrote:

I have a 1973 Spitfire and a Europa. I changed the bolt pattern to 4 x 100. I'm going from memory here but I think the original lugs had a 0.48 knurl so I picked up some 1/2-20 lugs with a 0.65 knurl. The original bolt pattern is 3.75 or 95.25mm on centre so you need to move the centres over about 2mm. You need a milling machine to do this since a drill press will never hold a bit straight enough. The first hub took a couple of hours but the rest went quicker. BTW Miata Daisies look cool without the centre cap

I've got a mill and I know how to use it...

Yeah, I guess I forgot who I was talking to.
Feb. 2, 2011 9:08 p.m. MrJoshua SuperDork

The stock rear suspension/drivetrain on the spit is crap and inadequate for anything more than the stock spit power. Swapping a rear subframe is cool and there are many options, but it would be similar or less work to build a new double a-arm setup front and rear. Another option would be to use miata subframes front and rear, but then you are basically building a whole new frame. The Miata daisies do look decent on a spit though.
Feb. 2, 2011 9:39 p.m. Giant Purple Snorklewacker SuperDork

The M20 is a very tall engine. I would think there will be a lot of clearance issues.

I might be tempted to think a WRX donor would make the same power with a much better fit and since it was a puffer to begin with - the whole thing will come running right out of the box. I'm not sure how the power gets to the rear wheels from that motor but there is probably a straight up trans swap that will do the job.

Or an M20 with a redonkulous hood scoop ;)
Feb. 2, 2011 9:41 p.m. Tom Suddard SonDork

I don't think the M20 is any taller than a GT6 engine, and I'm already planning on running a GT6 hood.

I'll look at my options for suspensions a little more.

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