Have I thought up a free meth injection system or will this not work?

[MJLamberson]

So you install a stock type manual fuel pump, The kind the carbed engines had, have the meth go through that, and to your cold start injector, which would be activated by a switch put into a manual boost gauge.

 

Any way to do this? would the injector pump out to little or to much meth? Im just playing around inside my mind currently, humor me.

[TrumpetRhapsody]

The stock mech fuel pump wouldn't put out enough pressure.

[MJLamberson]

The stock mech fuel pump wouldn't put out enough pressure.

 

to run a single injector? you sure?

[Evan Purple240zt]

Won't work.

 

Pump will also die a fast death at the hands of meth.

[BRAAP]

1) Meth is most likely not chemically compatible with the diaphragm membrane.

 

2) At the pressure the stock Mechanical Fuel Pump functions up to, the cold start injector would only trickle into the manifold, not a spray which is what you would want.

 

3) If the pump could be altered to function at elevated pressures taking advantage of the cold start injectors atomizing ability say in the 20-30 PSI range, the diaphragm membrane would most likely burst in a short period of time.

 

4) The cold start injector location is a poor location for single point injection. Cylinder to cylinder consistency would be quite poor. Mounting it ahead of the TB would more ideal.

 

5) Electric pump allows you to control when the system is pressurized vs being pressured the entire time the engine is running.

 

 

Personally, I see far too many cons to using mech pump with so many easier, quicker, more cost effective ways to accomplish this.

[ktm]

BRAAP beat me to it. Most methanol injection systems operate at close to 3 times the stock EFI pump pressures. Yes, 3 times the pressure. My FJO setup operates at 110 psi, others are closer to 150 psi.

 

You need the methanol to vaporize, not form droplets, hence the high pressure.

[MJLamberson]

Well there you go, I learned some new things today!

[Tony D]

Decal from 1970's vintage racing sled I once owned:

 

"Carburettors Equipped for Methanol Change Diaphragms After Each Racing Day"

 

That has not changed in 37 years...

 

If we want to parse the pressure argument, it 'can' work at any pressure, it just depends on the nozzle design. Bette Fog Nozzles make a nice impingement nozzle (stainless steel) that will give superfine atomization spray well below 60 psi. The key is to get the droplets fine enough that they readily vaporize and remove the latent heat from the intake charge. Given Methanol's low boiling point, you can get a relatively large droplet size and still have complete vaporization (compared to something like water, or gasoline, for instance). Ultimately the droplet size from the nozzle will be determined by the distance the droplet has to travel while changing state, and the airflow velocity at the injection point. The further you have to travel, and the higher velocity you have, as well as the higher heat, the larger the droplet size you can tolerate and still get total vaporisation. The modern systems using super high pressures (relative to older systems) allow you to place the nozzle almost anywhere and still get total change-of-state from liquid to vapor, removing the maximum ammount of heat possible.

 

In the old days, a carburettor jet, on a windshield washer pump, spraying into the turbo inlet gave the same results, having turbo outlet temperatures in the low 100F range, instead of 2 to sometimes 3X that value. But there is a lot of 'impingement and heat' going on in that system, as opposed to the stuff today where it comes in superfine mist for flashing in relatively low temperatures (allowing inlet temps below ambient when used with an intercooler)...and that is the final word on the high pressure: because it's so high, it can atomise so finely, it allows injection into low-temperature airflows and STILL remove heat from them.

 

 

But the stock pump? No. Cold Start Injector? No.