Me and my brother are working on plans to build a Locost 7 kit car. The engine I want to put together for it is a peripheral port 13b. He has machining experience and access to machine tools so I think we can do most everything ourselves. I do have a few general questions though.

I know that for a bridgeport engine, it is generally best to start with a 4 port motor because of the weird things that happen with the aux ports. With a peripheral port though, the original ports are closed off entirely so is a 6 port actually a better place to start for PP? I would imagine so because of the higher compression, but I don't know and can't really find any answers. I'm thinking IDA style intake with a Weber 51 or a DIY throttle body set (likely sports bike) and running megasquirt (I know a megasquirt tuning master, so that shouldn't be a problem)

Also, how does a PP motor react to a bit of spray? I'm thinking a 125 shot or something with a fairly nice punch. I'm looking for around 400whp+ (on spray) to put in this 1000lbs car. Attainable?

We're not building this car for any particular sanctioning body or race...(perhaps hill climbs) but just something that can kick some ***.

Edit: I figure I could expedite the entire process by just buying a wrecked S4 or S5 car. That way I can use most of the drivetrain and suspension from the car and not worry about having to mix and match parts.

 

first of all, congratulations. i love these builds from scratch with minimal input from "professionals".
generally speaking, 6-port is no better or worse as a starting point, unless you have specific plans and goals for your peripheral. for example forced induction and/or output goals may dictate what housings you use simply because they may be stronger. obviously compression can be tailored to your needs by obtaining the rotors with the compression you want.

in all honesty, my advice would be to start with the least expensive engine you can obtain in good shape. my logic is this: (1) it's your first PP project, you need to get used to the prospect of failure, and (2) most of the things that cause variances in the prices between the different years/models of 13Bs are irrelevant anyway because you're going to be boring giant holes in the rotor housings for use with custom or aftermarket intake systems anyway.
either setup is proven. i think it will come down to comfort and budget. however, at this stage of the game i wouldn't bother with a carburetor, but that's my viewpoint. however, as you said you're considering MegaSquirt, so i'd say go for the injection setup.
i don't know how big of a shot you can use, so i'll let someone with experience answer this one.

 

it would be a fun car!

i think either 4 or 6 port would be fine, ideally 4 is less filler, and that's less to break, but in the real world it hardly matters.

ideally you'd want the 9.7 rotors, but 9.4's would work too. build the engine with FD clearances, and it'll be totally fine for the rpm/power

as far as the intake goes, a P port has 2 intake tubes, so the weber or weber style throttle body is a very natural fit.

ive never used the MS, i did look into it, and its not sequential, nor can you adjust the start/end of injection, which are kind of important. it was one thing when the MS was $150, but you can spend $500 on one now

the carb actually runs ok, although when you change things on the MS its a keystroke, the weber is a pair of $5 jets... the carb gets expensive too

 

Start off with a second gen 13b N/A it has the larger style oil pump (greater volume).

 

Definitely.
A PP handles nitrous very well; the huge intake tubes and wide bending radii make it far more diifciult to achieve nitrous backfire. The biggest thing is nozzle placement with a PP, and direct port should be considered essential.
If your drivetrain will support a 125 shot, the engine definitely will. Personally, I would go for much larger jetted foggers (300 hp or so) and then use PWM to control power delivery under spray.

A megasquirt can easily be configured to provide the majority of safety features for nitrous:
- Nitrous engage above specified rpm
- Nitrous shutdown above specified rpm
- Nitrous activation only upon WOT
- Checkback circuit for the solenoid relays
- Lean-AFR shutdown
- timing retard upon engagement
- fuel map switching/ extra fuel upon engagement.
A window switch, WOT switch, and timing retard should all be considered essential parts of any nitrous install, and thus having to buy these extra features that are otherwise included in the MS package does significantly add to the cost of the carb set-up.

It doesn't matter what plates you use; although the S6 and late S5 plates are the strongest should you encounter detonation.

 

I think I'm going to try to find a S5 six port to start with.

 

Just watching an old episode of Top Gear and the Caterham r500 is quicker around a track than a Ferrari Enzo, Bugatti Veyron, and Zonda F (among many others) and it only produces 230bhp (around 200whp or less) I cannot fathom how insane one of these cars would be with 400whp. But I certainly want to find out

 

think this400 HP Lotus Exige ... but quicker.

 

Well it would have double the p/w as that car...

Ok I've been looking around for an S5 13b, anyone got any ideas on where to find them?

 

FD motor would work too, its got everything except rotors

 

Hard to find FD engines under 1k though. I'm lookin for something that needs to be rebuilt, so hopefully under $500.

 

I've been thinking about something quite a bit lately and thought I'd throw it out there. I had already started this thread on the topic so figured I'd write it here.

I've seen twin-choke carbs used in pp engines
I've seen holley carbs used in pp engines
I've seen ITB's used in pp engines

I have, however, never seen a mass-air powered peripheral port engine with a full plenum-style intake manifold. The biggest drawbacks to the PP engine is the drivability at lower RPM's (myth?) and the poor fuel mileage. Well when you are dumping that much fuel through a carb or ITB setup, it will always get terrible mileage no matter the port style. However, if you had a intake setup with mass air I think it could be tuned to run way more efficiently. Possibly have a throttle-position based fuel map, and secondaries in the intake manifold so that under normal driving conditions it is only getting a base amount of fuel and air. When you lay into it, the secondaries would open and another set of injectors could come on to keep up with the air demands. I don't think it could make as much outright power as a ITB setup, but if you could make a truly streetable peripheral port, it would be epic. Just kind of talking points right now, but tell me what you think.

 

i've seen plenum-style PP engines. i can't recall seeing any N/A though. to be honest, i would tend to think once you spend some time tuning with any decent EMS, you could get an acceptable (as long as your expectations are realistic) amount of civility out of your engine. though i have not built one as yet, i can say the technology for both the physical port timing and engine management has come a long way since the days of the unruly 2000-RPM-idling monsters of yesterday. i don't doubt that you could get a MAF-based system to run your engine well, but i also don't think it would be necessary to go out of your way to do so. these are my thoughts, at least.

 

MAF is attractive to me because of the flexibility it has to offer. You don't need to retune every time you change the inlet-pipe diameter and such. Also, I believe MAF is better to react to changes in altitude? I'm not sure if that is correct, as I can't recall whether a MAP-tune will compensate for that.

 

1000 kg maybe, I think 1000 lbs is impossible in an FC unless the whole chassis was made of carbon fiber/fiber glass.

As for choice of rotors, you can pick up some used N/A rotors in the B/S/T section, S4 rotors have a compression ration of 9.4:1 and S5s have 9.7:1

 

lol read the post again...LOCOST 7:

 

a twin choke carb = ITB.... they are functionally the same, ITB implies fuel injection

a PP engine is different from a side port engine. in many ways.

the first thing is the P port is more efficient than a side port at its tuned rpm, so a PP will actually get BETTER mileage @ high power than a side port. at low power.low rpm its out of its tuned range and will be worse than the side port.

mazda got about 6mpg with the 787B during the race. @700hp that's impressive! it would be tough to match that with a 13B @180hp!

second the port style gives very good flow between the intake and exhaust. also they open and close faster. this means that the intake flow isn't steady, and it doesnt seem to all be in the same direction! if i run mine, and pull the air cleaner off, the lid will be wet with fuel

so this makes plenum intakes hard because they interfere with each other. you almost want to run it like 2 separate engines.

maf might be possible, but the 787B used the TPS. o2 sensor won't work @low rpm/low load due to the overlap...

i've learned from mine that like a bridgeport if you give the engine some load, its happy. they idle @750 rpms... and that's with a CARB and distributor. the "bad at low rpm" thing is partly true, if you try to follow all the toyotas doing 12mph in a 45 zone, the PP will be unhappy. if you're not stuck behind a prius, and can let it run, its (and you) will be happy campers. with EFI it would be much better.

forget all the secondary/plenum/fancy b/s stuff, just build a ITB EFI engine, and you'll be quite happy.

worry about making it not loud without killing the power =)

 

Yeah I was just mainly throwing that up there to see what you guys thought. Isn't the plenum actually there just for the reasons you were saying though? (as in reversing pressures and such)

This will be just a weekend nutter-mobile and maybe a hill climb car (where there are no restrictions...i hate restrictions other than safety) I don't want it to be civil, I don't want it to be quiet. I want it to be the most unrelenting son of a bitch around.

So how is this for a game plan

S5 N/A 13B with stock internals
-Peripheral Port the housings
-Do a long primary exhaust system straight out the side
-Run only an alternator. Probably with an underdrive pulley to keep it from shredding

With a decent intake setup, do you think this can hit 275-300whp?

 

i think the PP might be too nuts for a plenum...

you'll be surprised the PP IS civil, it just wants to run.... if you try to drive it slow, that's when it'll buck... you'll be surprised at the torque it has too, even from 1000rpm, WAY WAY better than a side port

noise is a problem.

but yeah your plan is about right... the MFR engine is 300hp@9000 right out of the box, with 3mm seals and 9.4's....

using smaller ports will loose a little power, but it'll be lower in the rev range

 

Is there any benefit of running 3mm seals? I thought that was mainly for boosted engines? Aren't 2mm better for high-rpm?

 

yes 2mm is better for everything! the MFR 13B is from like 1981ish, they didn't have 2mm seals or 9.7:1 rotors back then...

 

Ohh ok I gotcha. I was thinking this was some new engine.

 

nah the newest racing engine is the R26B, and that's from 1991

 

Where do speedsource and all the other grand am teams get their engines from?

 

the one at sevenstock looked like a cosmo 20b, with the RB PP housings...

the other option is the 13G which is the racing 3 rotor.

mazdausa stocks parts for both. err you can still BUY all the stuff, minus a couple of things, but its like its a new design or anything