Say you wanted to build a budget BP

Say you wanted to build a budget minded naturally aspirated 1.8L Mazda Miata engine. What parts would you use?

The goal is a 175hp with broad torque. Can this be done?

Escort GT parts? Camshafts? Which manifolds? etc...

This is relevant to my interests.

Very relevant to my interests. My suspicion is one step will involve an aftermarket ECU. Also the higher compression pistons from the 01+ Miata. But what do I know?

I've been out of miatas for a bit, but I bet a 99' cylinder head will be involved.

I would say a '99 block and head, '99 rods and '01-03 pistons (supposedly 10ish:1 comp). Pistons would depend on price. If you found '01+ pistons for cheap, great. If you can't find them cheap, you can shop around and find Wiseco 11:1s for descent I'm sure.

If you were able to get a deal on machine work, I'd do a full balance and knife edge the crank. ECU option for Miatas I'm not familiar with, I do EGTs and Proteges mostly. But if you have someone close to you that can regrind cams, I'd do something fairly high lift, good duration, and a set of adjustable cam gears to sync them. On a stock ECU, I'm not sure what you could run, but without doing a lot of headwork, as well as utilizing the solid lifters of the '99 head, you might be able to go 260-275ish duration, maybe 216ish-228ish at .050. I would recommend changing valve springs obviously. If you did springs and retainers, you might get away with .370-.385 lift, but this is all just stuff that I'm pulling out of my ass, so IDK if you want to listed to me. Only cams I've ever dealt with are turbo cut, which is quite a bit different

Then of course a good racing header and a CAI that complies with whatever club you're racing with. Racing Beat would be a good start.

IDK if that helps because I only have done FI BPs, but it may get you started

I'm going to go out on a limb and say it probably won't be too cheap or even easily achievable.

http://solomiata.com/CheapHP.html

SoloMiata said: My new "street" motor with the above plus 11:1 compression (10:1 2001 +.020" pistons, .026" deck and .010" head shave), lightened/balanced/knife-edged crank, 260 degree cam, adjustable cam sprockets, ported intake manifold, +2.5 mm throttlebody, aluminum underdrive pulley, programmable ECU, and using 4.778:1 rear gears just netted 160 hp at the rear wheels with 125 ft lbs torque at just 2500 rpm. This level of power was not plug 'n play, I tuned the ECU and cam sprockets for weeks. Additional costs beyond the 'cheap' level was about $3000 for an incremental 50 crank HP. So, for a total of about $4000 (not including the original 1.8 swap, my installation and tuning time, or the over $600 in dyno time tuning everything), I have nearly the same power as a supercharger or mid-level turbo kit. See why a turbo or supercharger kit is much more cost effective.

I'd go the FrankenMiata turbo route for that kind of power from a BP. From what I've seen the BP can't compete with other powerplants (SR20 comes to mind) as far as easy naturally aspirated power goes.

word. you're looking for specific output of nearly 100hp / liter NA, which only comes with RPM. cheaper to add boost + intercooler + megasquirt + injectors.

AngryCorvair wrote: word. you're looking for specific output of nearly 100hp / liter NA, which only comes with RPM. cheaper to add boost + intercooler + megasquirt + injectors.

Yea, it seems as if you could get even some crappy e-bay parts for a lot of that, fix, and make work.

You even mentioned a few years ago about a copper gasket on a BP motor with boost.

(although, I'm aware of the exhaust-intake cam swap that is reported to get some pretty stong numbers out of a BP motor. Even the exahust cam out of an EGT will work, if you can find a good adjustable cam sproket. not 175hp, but getting there)

As long as you didnt need a broad torque curve I'd say integral cams would get you there. One of the 1.6L SCCA engines I worked over (10:1 compression, stock head, stock crank, race pistons) put about 150HP to the rear wheels on a mild tune. Unfortunately it was like a switch - at 5K there was less than 100HP; but from 5K to 8500 it was like a rocket.

Integral Cams

Broad torque & 175HP would have to be mazdaspeed turbo or super high compression.

KJ

How about mildly high compression (10:1 pistons?) + Moderate Boost + E85 ?

That should give you something akin to DILYSI Dave's Dyno Graph:

I've tried it. Are we talking 175 rwhp? Not cheap nor easy. The engines seem to plateau at around 160. I've got a 150 rwhp 1.6 that's actually quite streetable (Webcam 505 cams, 11:1 compression, Link ECU, custom header) but my 2.0 peaked out around 175.

The "exhintake" swap seems to be more legend than fact. I don't think I've come across a bona fide sucess story with it, and the biggest gain I've heard of was 8 whp after a lot of pain. Not bad at all, but I think the biggest appeal is that it's cheap.

If you want to do it with stock parts, use a 2001-05 engine. The VVT will need to be controlled - I'd use a Hydra myself. The VVT will fill in the bottom end. It won't have an effect on the headline horsepower number, but you'll pick up a lot of torque. Use the same intake manifold with the VTCS butterflies removed (NOT the same as hollowing out a 1999-00 intake, which netted absolutely nothing in my testing) and build your own header. Shave the head a bit to bump the compression. A good set of throttle bodies will probably unlock a few more horsepower as well according to my testing.

Naturally aspirated power is something you chase 1-2 hp at a time. Bill Schenker, who's got one of the top CSP Miatas in the country, has done a huge amount of detail work on his mill, investigating things like the exact length of the intake tract pre-throttle body. He's in the 160-170 range these days. So while the parts may be cheap, the dyno time is going to add up.

Integral Cams is gone, unfortunately, although I believe their grind programs have been purchased by another shop.

Or, buy a Voodoo II turbo kit. Until we started the V8 conversion on my Targa car, I had both a naturally aspirated 2.0 and a Voodoo II 1.6 in my garage. The peak power numbers were very, very similar but the 2.0 had more torque. However, the 2.0 also had a price tag that was at least four times that of the little turbo 1.6, which is a bone-stock 100,000 mile engine that's only had the valve cover off for a timing belt change. There's a reason so many of these cars are turbocharged! No need to change the head gasket, it's almost impossible to blow out a Miata gasket with boost. Usually you'll take out the rods or pistons first.

It never ceases to amaze me how this engine ain't much of anything till you put a snail on it and then it's a giant killer.

If you want to stay NA, you're better off starting with an FE3. It'll probably cost less in the long run even account for cost of swap to get to 175rwhp.

KLZE swap has been done, but it's more involved. But in stock form, you're only about 10whp at most away from your goal.

I think 175rwhp is doable on a BP, even if you don't increase displacement, but it wouldn't be that street friendly. You'd just have to go all "honda" on it and end up with 13:1 compression or something crazy.

My recipe for an n/a BP is just like a recipe for any other N/A car i'd build.

The highest compression pistons i could get and still run 93 octane.
Head work.
Big cams.
I/h/e.
Standalone.

Done. Will it have a large powerband? Probably not. Would it make power? Sure. Cheap? No.

I guess my answer to your original question taken to a "T" is: I wouldn't.

My apologies I should have stated that my "goal" is ~175 CRANK horsepower (125-130 rwhp) on regular unleaded. It will be used as a sporty RWD commuter that gets similar MPGs as my GLI (27mpg at 80mph, 31mpg at 65)

The project car in question is a little heavier than a stock Miata (~2625lbs) I do not own any of the parts to do the swap but as of 8:00am I own the car. I am not set on a built 1.8L but I would like to bolt it to a Miata transmission (I know a guy who has one for the right price) so it should be a B series engine. I also have access to a 1986ish RX7 transmission for a similar price if there is something that will fit that that does not involve magic spinning triangles (fuel mileage). If there is an easier (more tq/hp) engine that will get me to the promised land with a stand alone computer I would be receptive.

I also considered doing a V6 Ford/T5 swap (among other options) but it would too low in the MPG category but +eleventybillion on the torque/fun factor, on the table but not on my plate yet.

this is very relevant to my interests, given that I want to build a budget CSP-legal motor and have access to a complete engine out of a '99 Miata and the Mazdaspeed competition parts catalogue

Interesing project.

Which RX7 trans is available?

The reason I ask is that with the right gear set + rear ratio (all available to fit the Miata parts), you can end up with 1, 2, and 3 being almost identical to the Miata, 4 taller, and 5 a lot taller.

Why would that be better? with a turbo, you can have the same fixed gear performance, or better, with 1000rpm less. I've considered it for a long time. Never could pull the trigger, though. But the idea of 70mph at 3000 rpm vs. 4000 was very interesting.

John Brown wrote: My apologies I should have stated that my "goal" is ~175 CRANK horsepower (125-130 rwhp) on regular unleaded. It will be used as a sporty RWD commuter that gets similar MPGs as my GLI (27mpg at 80mph, 31mpg at 65) The project car in question is a little heavier than a stock Miata (~2625lbs) I do not own any of the parts to do the swap but as of 8:00am I own the car. I am not set on a built 1.8L but I would like to bolt it to a Miata transmission (I know a guy who has one for the right price) so it should be a B series engine. I also have access to a 1986ish RX7 transmission for a similar price if there is something that will fit that that does not involve magic spinning triangles (fuel mileage). If there is an easier (more tq/hp) engine that will get me to the promised land with a stand alone computer I would be receptive. I also considered doing a V6 Ford/T5 swap (among other options) but it would too low in the MPG category but +eleventybillion on the torque/fun factor, on the table but not on my plate yet.

Oh yeah, i'd be going FE3 in that case. 170hp to the crank, stock. I think the RX7 or Miata transmission work with it with fairly minimal work. I know in the FWD cars, you can use all the BP mounts save for one to drop it in.

FE3 swaps in BG chassis is somewhat common now, and pretty easy from what i understand. I doubt it'd be that much harder in RWD scenario.

F2T?

alfadriver wrote: Interesing project. Which RX7 trans is available? The reason I ask is that with the right gear set + rear ratio (all available to fit the Miata parts), you can end up with 1, 2, and 3 being almost identical to the Miata, 4 taller, and 5 a lot taller. Why would that be better? with a turbo, you can have the same fixed gear performance, or better, with 1000rpm less. I've considered it for a long time. Never could pull the trigger, though. But the idea of 70mph at 3000 rpm vs. 4000 was very interesting.

The transmission is from a "1986 or 1987 "Sport" package car" per the current caretaker. I know the car is not turbo, has 5 bolt wheels and has been treated like a Tijuana Taxi which is why it got parted out, I did drive it (3 years ago before it was parked and parting started) and the transmission "felt" good.

pres589 wrote: F2T?

Doesn't meat the n/a requirements, but assuming the car in question is an FC RX7, it's not THAT bad to do. Would easily give him quite a bit more power than he was looking for, while still meeting MPG requirements, though.

Errrrr... that should be "meet."

In reply to John Brown:

I wish I knew- the parts interchangeability page went away a few years ago.

According to the spread sheet I made for this work- my '99 has a 4.30 rear, 3.136 1st, 1.888 second, 1.33 third, 1 4th, and 0.814 5th.

and I chose gears that are supposed to go into that box and FD that went into the rear- but I'm not sure.

But in choosing a 86-91 RX-7 5 speed (3.415, 2.002, 1.366, 1 and 0.691) and a 3.91 rear end (can't recall where that came out of) I got a comparison, gear, Stock, modified- in rear wheel ratio:

1st- 13.48, 13.59

2nd- 8.12, 7.83

3rd- 5.72, 5.34

4th- 4.3, 3.91

5th- 3.5, 2.7

So 1-3 are pretty close, and 5th would lower a 4000rpm cruise to 3087 rpm. Gotta think that would do wonders for fuel economy.

I had been thinking of a turbo 1.6l. But could not figure on how to make the calibration production quality and realiability vs. my '99. so...

Eric

3k cruise RPM with an F2T would be a bit buzzy, FE3 probably similar. Don't know about BP, I think it would be better but I lack exposure. Need to drop another ~700rpm to have a nice cruise with an F2/F2T.

pres589 wrote: 3k cruise RPM with an F2T would be a bit buzzy, FE3 probably similar. Don't know about BP, I think it would be better but I lack exposure. Need to drop another ~700rpm to have a nice cruise with an F2/F2T.

FE3 is a much smoother motor... 3k rpms on it vs. 3k rpms on a BP would be pretty much a wash.

Any way you slice it, the F2T is kindof buzzy, period.