Post throttle vs Pre throttle

[ricekikr]

Is there a big difference between installing the meth nozzle pre vs post throttle?

I'm inclined to install it post throttle because there have been issues with it leaking into the throttle and messing up the TPS and Idle control. I understand that meth needs to be as far away from the throttle to provide the maximum cooling, but does it really make a big difference?

Does the checkvalve work well if installed post-throttle? Or will a solenoid be needed?

[Richard L]

This will depend on what type of system you have. Does you system have a solenoid valve to stop the flow instantly rather continue to dribble until the line pressure drop down to zero differetial.

If you run high percentage of methanol on your system, the residual spray (dribble) and cause pre-ignition problems on a few cylinders and methanol can ignite during the valve overlap period.

A check valve is a definate no no for post throttle applications.

[5mall5nail5]

This will depend on what type of system you have. Does you system have a solenoid valve to stop the flow instantly rather continue to dribble until the line pressure drop down to zero differetial.

If you run high percentage of methanol on your system, the residual spray (dribble) and cause pre-ignition problems on a few cylinders and methanol can ignite during the valve overlap period.

A check valve is a definate no no for post throttle applications.

Richard I just found this post of yours - a check valve is a defanate no no. Is that necessarily true? I just ordered 4mm check valves from Howerton for my direct port setup.

Thanks,
Jon

[Richard L]

Jon,

This is because a checkvalve does not stop dribble. If the methanol is allowed to contact the hot exhaust gas during the exhaust stroke, you will most probably create a good environment of pre-ignition. Use an inline to ensure there is no change of dribble. (keep the line to the jet as short as possible.

A number of checkvalves can be used in conjunction with the inline valve to stop liquid commuting between the jets on each runner.

[stevieturbo]

How can detonation occur during the exhaust stroke ?

And even fuel will still be injected on most performance engines, as they wouldnt use a throttle deccel cut ? Is there really much difference ?

[Richard L]

It is possible at the end of the exhaust stroke over lapping the commencement of the in take stroke. More pronounce on cam with large overlap.

It can take place either way, some hot gas is blowing into the inlet tract (short exhaust) or charge air and methanol is drawn into the cylinder by the vacuum created by the exhausting gas.

It is not detonation but pre-ignition mentioned.

[5mall5nail5]

Jon,

This is because a checkvalve does not stop dribble. If the methanol is allowed to contact the hot exhaust gas during the exhaust stroke, you will most probably create a good environment of pre-ignition. Use an inline to ensure there is no change of dribble. (keep the line to the jet as short as possible.

A number of checkvalves can be used in conjunction with the inline valve to stop liquid commuting between the jets on each runner.

Richard I am confused.

I picked these guys up from Howerton

http://farm9.staticflickr.com/8088/8375362948_731f5c2605_c.jpg (http://www.flickr.com/photos/67031861@N08/8375362948/)
Aquamist Check Valves (http://www.flickr.com/photos/67031861@N08/8375362948/) by Jon Kensy (http://www.flickr.com/people/67031861@N08/), on Flickr

Do I need something else?

[Richard L]

There are two types of dribble.

1. Line decompression:
A checkvalve will not stop this totally but helps to minimise it. There are two kinds of wmi systems, PWM valve (aquamist) and PWM pump (the rest). there is minimum dribble with aquamist because the line de-pressurise period is relatively short (milli-seconds rather than seconds) due to the sharp cutoff action of the inline valve. Using a small OD hose (4mm) has help greatly.

2. Siphoning effect between multiple jets:
During injection, every line to the jets are filled with fluid. Upon shutting off, the line fluid will be drawn out by delta pressure between jets. If you use multiple checkvalve, this siphoning effect is almost eliminated due the the delta pressure is blocked off by the action of the checkvalve.

Conclusion:
Checkvalve is important if you are using multiple jets especially when there are vacuums. We have heard quite a few extreme cases with manifold got blown apart. But this is rare. The amr (air/meth/ratio) has to be pretty close to 6.6: 1 for an explosion to happen.

Describe your current set up to me here.