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  #1  
Old 20-11-2004, 04:57 PM
Gelf Gelf is offline
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Default Pre Turbo Injection - How Much and When to Inject

Purpose of experiment:


Primary:

Determine the ideal amount of water to use and when to inject it.


Secondary:

Compare a single jet / HSV / FIA2 application to a twin jet / HSV / FIA2 application.

The single jet injects once every two revolutions (ingnition stroke on cylinder 3)

The twin jet injects once every revolution (ignition stroke on cylinder 2 and 3)



What are the desired effects of pre turbo WI?

Lower the inlet tract temperature.

Increase the efficiency of the turbo. Lower the turbo exit temps to as close to isothermal compression as possible.

And of course, in cylinder detonation control.


Negative effects of WI

Decreased efficiency of the intercooler, over injecting can saturate the internal surface of the IC, to the extent that it has virtually no effect at all.

What im looking for

Consistantly low turbo exit temps
High IC efficiency
Lower than ambient throttle temps in the summer, but not less than (??) for the winter ((??) not sure what the lowest temp should be yet).
Maximum effect from the east amount of water injected.

Water Injection turned off:




Single Jet set ups at fixed boost trigger @ 12/13 psi:












Twin Jet set ups at fixed boost trigger @ 12/13 psi:














Twin jet set up using 0.4 and 0.5 Triggered @ 4, 7, 10, 13, 14 and 15 psi: I would have used a pair of 0.4, but i dont have a pair yet.















Conclusion:

In my opinion, using a twin jet setup with the smallest jets possible and triggered at 4 psi gave the best results. I want to see 0 psi results.

I know most people say inject as late as possible, but these results would suggest otherwise. Im thinkin that when injecting late, the effects are felt after the event of high boost, too little (or too much) too late. Triggered early on using a system like 2d, the water is metered effectively from low to high rpms, as with the fuel, producing smoother transition in inlet tract temps.

I will continue too experiment now using twin 0.4's for winter and twin 0.5's or 0.6's in the summer.

I will measure differences in performance at different boost points using an accelerometer and post results.

Initiall experiments at 4 psi show no increase in lb - ft and a 2 or 3 drop in bhp, at WOT and 3/4 throttle opening.

Lower exhaust gas temps reduce the maximum turbo rpm's :?, but now the max boost setting can be increased :?
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  #2  
Old 21-11-2004, 09:30 AM
PuntoRex PuntoRex is offline
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I had the similar experiences about the trigger point.

Currently I use 1*0.5 at pre-turbo & 1* 0.6 at pre-TB, triggered at 10psi, max boost around 18~20psi.

I can be sure that the turbo spools up much more quickly in the 10~20psi region than the 0~10psi. Probably, that's the work done by water.

Which stops me make it earlier is the worse atomization in the low DC injection. I'm a little worrying about the larger droplets caused by this, especially pre-turbo.
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  #3  
Old 21-11-2004, 02:01 PM
Gelf Gelf is offline
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Quote:
Originally Posted by PuntoRex
I had the similar experiences about the trigger point.

Currently I use 1*0.5 at pre-turbo & 1* 0.6 at pre-TB, triggered at 10psi, max boost around 18~20psi.

I can be sure that the turbo spools up much more quickly in the 10~20psi region than the 0~10psi. Probably, that's the work done by water.

Which stops me make it earlier is the worse atomization in the low DC injection. I'm a little worrying about the larger droplets caused by this, especially pre-turbo.
Im not too sure what my water pressure is set at now, i need to get a couple of pressure gauges to monitor that both systems are working and set to the same pressure.

I ve noticed and i think it may have been yourself that said if the pressure is set to high the HSV starts to behave strangely, like the flow is being restricted.


I want to set mine to the highest permissable pressure to ensure good atomisation.
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  #4  
Old 21-11-2004, 11:17 PM
JohnA JohnA is offline
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Default Re: Pre Turbo Injection - How Much and When to Inject

Quote:
Originally Posted by Gelf
....What im looking for

Consistantly low turbo exit temps
High IC efficiency
These two are kinda mutually exclusive though:
The lower the turbo exit temps, the lower the efficiency of the intercooler.
This you can see clearly in your datalogs. The more water you inject, the lower the 'after turbo' temps, but the effect on 'throttle' temps is nowhere to be seen.
Single 0.4 jet @ 12psi resulted in similar throttle temps as both jets triggered at 4 psi (a lot more water in the latter case)

Quote:
Lower than ambient throttle temps in the summer, but not less than (??) for the winter ((??) not sure what the lowest temp should be yet).
The ideal intake temp at the throttle is around 40C mate, certainly no less than 30C
Quote:
Maximum effect from the east amount of water injected.
In that case from your graphs I'd say 0.4 jet at 13psi

Quote:
In my opinion, using a twin jet setup with the smallest jets possible and triggered at 4 psi gave the best results. I want to see 0 psi results.
I don't know how you reached this conclusion.
In any case, intake temps are not the whole story, especially if they max at 30C without WI :wink:
To me it looks like your engine setup at these ambient temps needs no W.I. for lowering intake temps.

It could be a different story if power is measured with different jets, while you run higher boost pressures. That would mainly reflect the advantages of in-cylinder cooling, which I'd think would be far more important than chargecooling in the winter.

Very interesting post, by the way.
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  #5  
Old 22-11-2004, 01:42 AM
Gelf Gelf is offline
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Default Re: Pre Turbo Injection - How Much and When to Inject

I knew this was going to be controversial :lol:
Quote:
Originally Posted by JohnA
Quote:
Originally Posted by Gelf
In my opinion, using a twin jet setup with the smallest jets possible and triggered at 4 psi gave the best results. I want to see 0 psi results.
I don't know how you reached this conclusion.
I'll try to explain, i said

What im looking for (a combination of things)

Consistantly low turbo exit temps

Comparisons between no WI, 0.4 @ 13 psi and 0.4 and 0.5 @ 4 psi.

I think the 0.4 and 0.5 jets @ 4 psi does just that when compared to no water injection and the single 0.4 jet @ 13 psi.



High IC efficiency Maybe i should have said highest efficiency possible from lower turbo exit temps.

Comparisons between no WI, 0.4 @ 13 psi and 0.4 and 0.5 @ 4 psi.

The 0.4 and 0.5 jets @ 4 psi generally showed the lowest IC exit temp (to be expected), while the 0.4 @ 13 psi faired worse than no WI.



Lower than ambient throttle temps in the summer, but not less than (??) for the winter ((??) not sure what the lowest temp should be yet).

Quote:
Originally Posted by JohnA
The ideal intake temp at the throttle is around 40C mate, certainly no less than 30C
Comparisons between no WI, 0.4 @ 13 psi and 0.4 and 0.5 @ 4 psi.

Granted, on this comparison both the 0.4 @ 13 psi and 0.4 and 0.5 @ 4 psi had similar results on occasions, but the 0.4 @ 13 psi showed temps going much lower, dipping as low as - 7 C. No WI wins this time, but the 0.4 @ 13 psi faired the worst.


Maximum effect from the east amount of water injected.

The 0.4 and 0.5 @ 4 psi does use more water than the 0.4 @ 13 psi, but in my opinion gives the best result when all things are considered. Expescially if your considering removing the IC all together.



Quote:
Originally Posted by JohnA
In any case, intake temps are not the whole story, especially if they max at 30C without WI
To me it looks like your engine setup at these ambient temps needs no W.I. for lowering intake temps.
I agree on this point, but im trying to set up before i get boost remapped. If i have WI set up, the RR operator may push the boost envolope a bit further.



Quote:
Originally Posted by JohnA
It could be a different story if power is measured with different jets, while you run higher boost pressures. That would mainly reflect the advantages of in-cylinder cooling, which I'd think would be far more important than chargecooling in the winter.
I agree and will do so once boost has been remapped.



Quote:
Originally Posted by JohnA
Very interesting post, by the way.
Thanks, its good to have someone to debate with
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  #6  
Old 22-11-2004, 09:42 PM
JohnA JohnA is offline
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Remember that intake temps consistently below 20C at the throttle will rob you of power. If that is true under boost as well, then you're compromising the engine's efficiency.

Older car designs used to have the air intake close to the exhaust manifold on purpose. Fuel injection can produce rich enough mixtures to make this a practice of the past, but the reality is still that cold manifold and cylinders damage atomisation.

Of course if you're thinking of ditching the intercooler (a brave idea!) then injecting at 4-5psi is a must.

keep up the good work!
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  #7  
Old 27-11-2004, 10:36 PM
masterp2 masterp2 is offline
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WOW! Excellent work!

Totally impressed.

I am getting set to inject a v-8 duramax turbo-diesel with WI, also pre-turbo and post-CAC (charge air cooler, IC, sorry about the language). This is a workhorse vehicle in need of supplemental cooling in extreme conditions.

Your charts will be helpful. I have set out to use a modulated 1st stage for water savings and activate the full 2nd performance stage with a throttle switch. The modulated 1st stage might consist of 1 .3 nozzle pre-turbo, and (2) .3 nozzles post CAC (or just post CAC nozzles). The performance 2nd stage might be 2 additional .3's pre-turbo.


thoughts?

Thank you for this research.
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  #8  
Old 29-11-2004, 11:03 PM
Gelf Gelf is offline
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Quote:
Originally Posted by masterp2
WOW! Excellent work!

Totally impressed.

I am getting set to inject a v-8 duramax turbo-diesel with WI, also pre-turbo and post-CAC (charge air cooler, IC, sorry about the language). This is a workhorse vehicle in need of supplemental cooling in extreme conditions.

Your charts will be helpful. I have set out to use a modulated 1st stage for water savings and activate the full 2nd performance stage with a throttle switch. The modulated 1st stage might consist of 1 .3 nozzle pre-turbo, and (2) .3 nozzles post CAC (or just post CAC nozzles). The performance 2nd stage might be 2 additional .3's pre-turbo.


thoughts?

Thank you for this research.
Thanks

I think a rpm switch and/or throttle position switch is a good idea, to restrict low boost, low rpm injecting when the size of the water droplets could prove to be too large.
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  #9  
Old 07-07-2007, 08:04 PM
masterp2 masterp2 is offline
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its been 3 years!

I thought I would add something that might revive this thread. It is specifically relating to observance of increasing CAC out temps with WI, and then subsequent lowering of charge temp at the the throttle location. It occured to me, in most cases with no WI, that these temps will be almost identical at all times. Only transport occurs from the CAC outlet to the throttle, no air "treatment". There is probably a modest pressure reduction.

It has been widely stated "CAC efficiency drops with WI". I agree, but I don't think it expalins what is observed, ever increasing CAC out temps with increasing water flow rate. I believe what you are seeing is the endothermic affect of vapor condensing in the CAC. This would have the opposite effect of evaporation, a heat up effect.

So why is throttle plate temp dropping past the CAC out? Pressure drop. Lower pressure is experienced the further downstream. And there is re-evaporation dropping the temp.

whatchya think?
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  #10  
Old 08-07-2007, 08:38 AM
Richard L Richard L is offline
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This is such a good thread, I think it has to be a sticky.
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