[DML] Re: Engine Conversions? [long]

[William T Wilson <fluffy@xxxx>]

On Fri, 21 Jan 2000, vsaini wrote:

> need a car that will at least perform as well as my crappy (crappy to
> me) 1991 300zx N/A... My previous cars were Rotary.. and i was

I think you could equal that performance just with a bolt-on turbo kit, or
with the new headwork modifications coming out of DMC Houston. The
naturally aspirated 300ZXs are ... well, not fast. :}

> wondering what it would cost and entail to convert a D' to a 13B
> Sequential Turbo like the newer RX-7's or even the monsterous 20C

I've put a lot of thought into rotary conversions (I think I will be
starting one in June or July, when I hope I'll have the money together). 
It boils down to a few things:

1) Cooling. Rotary engines require an oil cooler. Fortunately, an oil
cooler is available to fit the DeLorean chassis, designed to cool the
automatic transmissions. They will also require an upgraded radiator. PJ
Grady's radiator upgrade might do the trick. Unfortunately, the
possibility that the A/C radiator might have to be co-opted to help cannot
be ruled out. Rotary engines must not be allowed to overheat, so care
must be taken.

2) Transmission. Though an adapter for the Renault unit could be made, it
is suboptimal for several reasons. There is no positraction function in
the Renault transaxle. In addition, it is strong enough for only 250-300
HP. Finally, the gearing is very tall at approximately 3.2:1. This is
great for a torque-laden V8 motor, but it is too tall for a high revving
rotary (and *way* too tall for the very high revving S2000 motor that
someone else mentioned). Mazda uses 4.1 or 4.4 rear ends in their rotary
cars. I would suggest substituting a Porsche G50 transaxle (for less than
about 350 HP) or a G50/50 transaxle. A wide variety of gear ratios and
accessories are available for these 5 and 6 speed units. Unfortunately,
the G50 has a rather poor positraction function, whereas the G50/50 is
very heavy. Either should fit (the G50 is a little bit smaller).

3) Engine management. A Haltech, Motec, Electromotive, or Wolf3D engine
computer would have to be used with the 20B motor, and probably wouldn't
hurt even with the 13B (though a stock Mazda ECU could be used there, and
they are plentiful on the used market because Mazda keeps recalling them).
The super-computers are very expensive.

4) Cost. A used long block 20B sells for a whopping $3500 to $5000, a
long block 13B for about half that. Many parts will have to be custom
made. And people were complaining about the cost of the Northstar
engines! In comparison, a new Chevy crate V8 is about $1000,
unfortunately, it's just too big. :}

5) An intercooler would need to be set up. An air to water intercooler
could probably be shoehorned into the front somewhere, and would probably
be the simplest, as airflow is plentiful up front. This type of
intercooler is surprisingly lightweight, but it has to be done.

Of course there are advantages - the rotary motors are light, very small,
have a low center of gravity, and JZD wanted to use them in the DeLorean,
but it didn't work out. The power potential on the 3-rotor engines is
almost unlimited.

I would not suggest trying to use a sequential turbo system. The
sequential turbo system as used by Mazda is very complex (more than 70
vacuum hoses and dozens of moving parts), horribly unreliable, and works
well only with the stock system of catalytic converters, intake, exhaust,
and turbos, all of which would be different here. When RX-7s are modified
beyond the stage of simple exhaust changes, the sequential setup becomes
uncalibrated, resulting in uneven boost levels. The power benefit to the
sequential system is not that great - just stay away, for the sake of
simplicity.

Mazda has a new rotary motor coming - a 2 rotor engine the size of the
13B, but a radical new design capable of making over 280HP *naturally
aspirated*. A turbocharged version would easily make 400 HP, which is the
upper limit for the current 2-rotor engines. This would be a much simpler
setup than a 3-rotor for comparable power. Unfortunately, it probably
won't be sold until late 2001, though prototypes already exist.

> the answer for the D'.. perhaps another engine? good old pistons.. but
> something more reliable and compact.. say 300zx TT engines?

The 300ZX engines are long - I doubt they would fit. The DeLorean can
accomodate 4-cylinder, V6, and some small V8s, but inline 6 engines are as
a rule going to be too long.

> These are just my stupid views.. but hey.. i need the power.. i dont
> want to eat $H!T from Camaros and Mustangs.. you know how it is..

Just be careful - you don't want to actually be using the DeLorean's
advanced safety features. :}