DOHC B6 Information

[jhntu]

well if your home is near my home it's out in the front yard and the hood is unlatched so feel free. as long as it runs good i have no plans to dig into it. it may be difficult to even source a valve cover gasket. a lot of parts are unique to the 1.3 BJ that do not cross to a B6D or B3. even the oil pan is different but that may just be baffled. the bore is the same as the B6D (78.0mm) and uses the same rings but the pistons are unique. some specs from wikipedia and other sources:
BJ - 87hp @ 7000 rpm. 72 ft/lb @ 4500 rpm. 78.0mm bore x 67.5mm stroke. 4.058 final drive ratio
B3 - 63hp @ 5500rpm. 75ft/lb @ 3500rpm. 71.0mm bore x 83.6mm stroke. 3.777 final drive ratio

Found this from the land of the rising sun

http://www.goo-net.com/ipn/catalog/FORD_JAPAN/FESTIVA/3500640/index.html

[Advancedynamix]

I'm curious about this, what could provide longer last high power production in a b6 setup. You say with the right intake the b6ze can rev to 7k, so I'm curious, for the same peak power numbers, would it be better turn the boost up and shift at 6k, or turn the boost down a bit a run to 7k

That is a great topic to bring up.
A turbocharged engine can make more usable TQ at a lower RPM than an N/A engine OR it can be used to increase the TQ over a wider range than an N/A engine. It all depends on th design of the system.
There is no generic "correct" answer here, but an answer for every unique set of requirements. Building an engine system should be done with utmost consideration for the application. A Festiva is a very lightweight FWD car, and therefore doesn't benefit from a low end TQ as much as it does from high end TQ when over twice the factory TQ is desired. This is why I bring up shorter stroke benefits on this site. If we were putting one of these engines into a heavier RWD chassis then my suggested combinations would be drastically different. However, this is a Festiva forum and an engine thread which was is focused on swapping these engines into a Festiva.

I strongly believe that a broader and smoother TQ curve will propel a Festiva faster ,on roads and on a road coarse, than a narrower TQ curve (even if the Narrower TQ curve provides more TQ). This is due to the dynamic of the vehicle while being driven. These cars thrive on a momentum style of driving and the more shifting that has to be done, the more often you lose momentum and upset the car. For example, take 2 engines that make the same HP bolted to a G15mr gearbox;
1. 180hp 170ftlbs at 8000rpm with a 100ftlbs available at 3000rpm and a linear curve to 7000rpm where the TQ flattens till 7700 or so.
2 180hp 180ftlbs at 5800rpm with 100ftlbds available at 2500rpm and a liner TQ curve to 5500rpm where it drops off to balivion (with Mike Tyson).
Engine #1 will be boring to drive and feel slow, but it will preserve tires and preserve the driver.
Engine #2 will feel faster to the novice driver, and will be more exciting to drive. This power curve will require more shifting and be harder to use in technical driving situations.

At the end of the day, engine #1 will dominate at 80% of the road coarses or fast road drives with an equally skilled FWD driver in an equally prepared Festiva. This is because the car isn't only being used on a theoritical incline straightaway, like many engine builders seem to design for (linear loaded Dyno). The engine is a dynamic part of a complex system which encounters thousands of variables with each passing lap or daily drive. Big numbers that happen fast don't always provide the desired result. Both cars will accelerate at nearly the same rate to 130mph in a straight line, but when you throw corners into the mix you will see the shortcoming of shorter power curve in a FWD car.

Engine #1 is a turbocharged DOHC B3(theoretical gt2560R @16psi), Engine #2 is a stock B6t with 16psi of boost and Methanol injection.

[F3BZ]

Hmmm. maybe a GTX and a blank check will be arriving at your house soon.

[sketchman]

^lol

You know you want to.

[TorqueEffect]

It's a real shame that every single B6 variant all use completely different headgaskets, so no hope for just doing head swaps.

Looks like if I want DOHC power, I actually have to swap in a DOHC engine.

[bhearts]

That and not having 4 valve piston reliefs. And something about an extra oil return port that a sohc block doesn't have.

[Advancedynamix]

It's a real shame that every single B6 variant all use completely different headgaskets, so no hope for just doing head swaps.

Looks like if I want DOHC power, I actually have to swap in a DOHC engine.

There are a lot of differences between the single cam and the dual cam b6 engines. The DOHC b6 was specifically designed by Mazda to be a world rally car engine from the beginning. This intent is obvious with the construction and design of it's parts. It is a thoroughbred race engine that was detuned for street use. The single cam engines are economy builds. Mazda doesn't make junk, so even the lowly b3 is a strong little econo pump, but the B6DOHC engine components make the b3 components look like tinker toys.
The BP is even more robust than it's older and smaller brother, with a monster forged crank and girdled main caps in later variants.

[jhntu]

Sorry to slightly hijack.. But in the dissecting a gtx thread, there is a gasket kit for the BJ and it refers to the B6D as the same gasket for the rocker cover.

[stanbu]

I see that the festiva is the wa model. Do you know whether the DOHC motor will fit the WB 95-97 model.

[sketchman]

My SOHC has 4 valves. You guys just swapped the wrong SOHC.

I kinda wonder how much in common the ME has with the D in the same displacement. The ports look very close to D design, and of course the 4 valve CC.

I'd imagine with a healthy cam the MEs would really come alive. Mine hauls as it is. Can't wait to feel it boosted.

[bhearts]

http://www.ebay.com/itm/1989-1993-MAZDA-MIATA-EUNOS-ROADSTER-1-6L-B6-CAST-IRON-TURBO-MANIFOLD-/121637561740?fits=Make%3AMazda%7CModel%3AMiata

this looks pretty nice. i wonder if one could fit a turbo on top in a festiva like they do in a miata.

[jhntu]

With the right custom exhaust, anything is possible.

[Advancedynamix]

I see that the festiva is the wa model. Do you know whether the DOHC motor will fit the WB 95-97 model.

It should fit better. I don't know for sure about hood clearance, but I do know everything will bolt up, or there are Mazda parts at the salvage yard that will make it bolt up. The engine mount is the only tricky part.

[Advancedynamix]

http://www.ebay.com/itm/1989-1993-MA...CModel%3AMiata

this looks pretty nice. i wonder if one could fit a turbo on top in a festiva like they do in a miata.

It may work, but would require some creativity for sure. Possibly a Kia g series trans to tip the engine? It definitely would require some custom upper radiator support mods, especially if your engine is mounted forward.

Here you can picture the amount of room you'd have for that top mount setup.

[sketchman]

Mine in the ME will be top mounted. Not log though, tube manifold. It's almost together. Another day and it'll be done. It's gonna be tight. Wouldn't want a wide DOHC head to make it worse.