I am building a 2nd gen N/a for a Group 5 Rally car. I want to spend the money (but not overpriced) on an engine from a reputable builder. I need someone that I can talk to about what I need and want, and someone that has the experience with RUNNING their engines and can help me peg down what kind of engine parts/porting I need. Peak horsepower is useless if it falls on its face everywhere else. Need that compromise of power, torque, over rev, and reliability.

I would like to keep the price under 6k.....reliability is an emphasis since "you must first finish to finish first"

My initial thoughts:
small bridgeport with s5 n/a rotors, built to rev as high as possible (reliably) without going to ceramic seals, and then actually run the engine about 1-1.5k lower. A carb and manifold setup for simplicity and distributor (may go to EFI after a couple seasons).

Any input on engine builders, or engine configurations would be appreciated! Thanks

 

what are the rules for group 5? are you limited to power to weight? or porting style?

 

Gp5 is awesome, basically the only drivetrain limitation is that the engine needs to be under 5.1l adjusted displacement. One sanctioning body requires that the engine be derived from something that the car's make sold (so a 2.3 Ford is acceptable since it was used in Mazda B2300s) and the other permits any engine swaps.

Also, if the car originally had a catalyst, it is required to have a catalyst-like device somewhere in the exhaust stream. (Notice that Andrew Havas's FB is a "1979", although the floor and firewall may have actually been a '79 at one point)

Havas's engine, incidentally, was a home built 13B peripheral port with stock 3mm iron seals for reliability, just keep the RPM below 8000rpm.

Unlike Open class, sequential boxes are allowed and turbos do not require restrictiors, but unless your name is Burmeister then nobody ever actually goes this far...

 

what adjusts displacement? how much HP can you use, really? actually fat powerband is probably better than peak hp huh?

power level desired dictates the rest of the combo, IMO

 

porting, turbos, # of valves (for piston engines obviously) etc

Hell I'll build you a gnarley PP engine for 5,000 including parts.

 

General wisdom is that over 250hp is useless with 2wd on gravel/dirt. More than that and you're just tearing those nice cheap (ha!) rally tires up. Which is why they did away with the turbo restrictor for 2wd cars... the ground is the limitation.

When rally cars started making over 250hp with good torque (and not 250hp from a 1.6l N/A engine) is when AWD became an advantage, FWIW.

FYI, it only took 6 *runs* on the gravel at Tulsa with 180hp to turn a pair of Michelin rally tires from sharp to rounded off nub garbage. You could feel the tires degrading during a run. I couldn't imagine doing a stage rally, my wallet would implode

I think the multipliers are 1.8 for rotary, 1.7 for forced induction (or maybe it's the other way around) and there's a multiplier for multivalve and a demultiplier for pushrods. I think it works out that the absolute largest pushrod engine you can run is 6 liters, the biggest DOHC turbo engine is 3 liters, and whatever in between. Almost nobody builds to these limits because too much displacement makes the car harder to drive. (Search Youtube for Mike Hurst's 358ci Mustang or John Lane's 600+hp Volvo... they mainly excel at destroying tires and not posting fast stage times)

 

if 250hp is a limit, then there are a few choices that would work.....

1. stock FD engine/turbos its got the flattest power curve..... the stock ECU works with the cat. its just complex.

2. P port, but tune the intake and exhaust for low/mid range. cat is going to be hard with this one... its going to melt, often

3. Rx8 engine.

 

the whole cat thing really sucks...

 

Turbo engines have been done (Cable Rhodes is the first person i can think of, he ran a Turbo II) but keeping them cool is a huge problem, even with the airy FC engine bay.

You just use a motorsports style "catalyst" with a stainless steel substrate that's maybe 3 inches long, and you put it at the very end of the exhaust. And you make it easily replaceable.

If you think p-ports are catalyst unfriendly, try an Open class engine with harsh levels of antilag. Putting them at the very end of the exhaust helps them live. (Group A Escorts had them by the rear diff, and they had NASTY antilag, like melt the exhaust manifold in a half hour levels of antilag) If you watch WRC, you can see the catalyst substrate glowing in the tailpipe, and a constant 2' blue flame out the pipe during night stages...

The US rule used to be "car must have a converter". So people zip-tied them to the rollcage. Then the rule was "must be able to detect at least a 1 degree temperature increase across the converter". This is easy to fake with different thickness pipes (no cat) - just make the front more insulated than the rear by whatever method you choose. Rear hotter than the front = legal.

Now they want to be able to see the substrate.

 

it's wise not to let builders know your top end price range, they will rape you on everything. $5k is a chunk for even a built non turbo engine, you can get close to a fully functional drivetrain for that price.

i would probably suggest a semi PP FI setup with a standalone. for the cat run a cutout to a metallic substrate cat, it will function but most of the exhaust will go straight out the back.

 

The rule, at least for Rally America, is that all exhaust must go through it...

It's really a non issue. N/A rotaries got nothing on a high compression 2.3l piston engine running crazy levels of boost and antilag to keep the turbo spooled

 

i guess turbo is the way to go then.

 

peejay, were u the halfbridge 1st gen at Tulsa? I talked to you briefly. I was racing stock AWD in the 2009 impreza (blue/silver) #669.

I do not want to go the turbo route for multiple reasons:
1. Initial cost of the turbo setup and standalone
2. The cost of keeping a turbo car running compared to N/A. Blown turbos,more wear and tear on components, cooling, etc......as a racecar it is fairly significant
3. Racing at different elevations I would worry about the tune (seeing how a turbo rotary's reliability depends on tune)
4. Probably something else I cannot remember.....

I would not tell the engine builder my budget, however I expressed that here. I want a builder that can build me a bullet proof engine as possible, with an understanding of the performance I want out of it.... I would be happy with around 200-220 hp as anymore isnt too practical on gravel..... but those tarmac events it sure would be nice against the other group 5 cars which are probably all turbocharged.....

 

Looking at some of the popular builders I know of, a rebuilt bridgport with all the oiling mods is going to run about 5k. Any suggestions for builders? I have been out of the rotary loop for a few years so only several came to mind while searching.... who has the best bang for the buck, while building top quality engines, with a thorough understanding of the performance their particular setup will give??? I would consider a standalone setup for N/A.... as it is about the same as a carb/manifold or ITB setup it looks like. Still want to avoid turbo for reliability reasons

 

if you're spending that much on oiling mods, you're looking in the wrong direction and already taking a hit to your "best bang for your buck".

 

if you are starting without a core motor, 5k is probably about right. i would start with an FD core, new seals, and rotor housings, and it would be nice to have new 9.7 rotors.

again if you're starting with nothing, EFI and a carb are about the same money. so EFI is the better choice... i checked the EGT's on my vert, which is stock, and they only hit 820c, which is almost cat friendly.

i don't know about specific builders, but the big problem is always that as a customer you never know what you get when you buy a rotary. did you get new housings? seals? what were the clearances? our piston engine guy gives us a sheet with the before measurement, the factory spec and the after measurement.

 

Kick ***. Yeah, that was me. (The lanky ponytail/glasses dude, not the lanky non-ponytail/non-glasses dude)

The engine you saw is about 180hp at the crank. Been running it all season, about 10k miles plus don't know how many rallycrosses. Still has the same compression as when I assembled it... with 100% used parts from the same core engine. It'd make more power but I'm keeping revs below 8k because of the iron 3mm seals.

200-220 is easy for a half bridge engine, make good torque everywhere so you don't *need* an expensive gearbox. Flexibility is awesome. Build it with 2mm seal rotors and you can use iron seals and use some revs, although I'd still keep things under 8500 sustained, 9400 or so absolute max.

The biggest keys to reliability are making sure the air going into the engine is CLEAN, meaning no vacuum leaks *anywhere* including air leaks in the airbox/filter itself. Making sure the coolant stays under 210, which also entails making sure the water pump stays turning and pumping water (the biggest problem I've been having, think it's finally solved), and making sure the oil stays cool.

Don't worry about the cat. Nastier engines have to run them too and they deal with it. Just run a motorsports steel-substrate "cat" at the very tip of the exhaust system, and make it easy to R&R in case it gets damaged or clogged.

 

There are a hell of a lot of rotary guys with pony tails and glasses. Am I missing something with my image?

Go turbo, you can get a hell of a nice powerband with the right porting and setup if you want to keep it under 300 whp. Plus Haltechs have some pretty neat anti-lag setups, and it can give you some flexibility to turn the boost up for tarmac events.

 

On dirt or gravel, the amount of torque that a turbo engine makes is crazy. Good throttle modulation is key.

Locally, we rallycross on claylike topsoil. Not used to running on gravel at all. If we ran on gravel at the low speeds of rallycross, I'd tone down the power as even 180hp is just instant wheelspin and shredded tires at 50-60mph. I can actually put down power in 2nd gear locally, not so at Tulsa.

Antilag 2wd setups have been tried... the people who've tried it says it's a waste of time, the amount of instant torque you get is explosive and really needs AWD to be able to use. And the more you're off the throttle with antilag, the more you kill turbos, it's the difference between eating a turbo a day and a turbo a season.

(Is there any wonder why Open Light is getting to be such a popular class? It's basically Open but with no forced induction allowed)

 

Thanks for the input guys. I have a wrecked TII that i am stealing the drivetrain and brakes from for even more durability(and engine for core). The turbo route sounds enticing I am just worried about reliability....
but bang for the buck maybe just a turbo streetport with a turbo that could make like 200 hp at like 8-10 psi to keep it reliable, and then swap out to a lil bigger turbo that could put out more like 300 hp for tarmac or GRC or pikes peak....

Does anyone forsee any tuning issues with traveling around the country at different elevations and a turbo engines reliability? Does the barometric correction do a good enough job?

I have my own opinions on this whole subject, it just helps to hear other people's thoughts, ideas, and to think "outloud" with a discussion.

 

^ About that last statement, that's what the forum is all about! That's why I love lurking in the N/A forum (even though I've never really messed around with any N/A rotaries), people are very open-minded, thoughtful and patient.

And with today's turbo technology, you can have a very fast-responing turbo that performs very well at both 200 and 300 hp without the need to switch. If you are considering any kind of high altitude, I would highly suggest going turbo. It just isn't possible to make-up the lost power from altitude without forced induction. But I promise, that's it for trying to sell you on turbos, this is the N/A forum dammit!

 

200hp@8-10psi you could just run the engine 100% stock except the exhaust. since you're rebuilding it put the FD oil pressure regulator, and baffle plate in. use a bigger fuel pump and call it done.

i'd even run the stock ECU.

if you want more, its a compressor wheel swap away