How much "extra space" does alcohol actually need?

[Leon Sterett]

H o l d o n !!!!!!!!!!!!!!!!!! alky has its own oxygen molecule, gas does not....bigger would only be if the alky engine is producing more power than the gas engine and therefore the cylinder demand is greater. Bigger means you slow down velocity and kill torque and lower your rpm power band.

Leon

[ozrace]

H o l d o n !!!!!!!!!!!!!!!!!! alky has its own oxygen molecule, gas does not....bigger would only be if the alky engine is producing more power than the gas engine and therefore the cylinder demand is greater. Bigger means you slow down velocity and kill torque and lower your rpm power band.

Leon

Leon, if you go back and read the reasons for the bigger port requirement, you will see that you are not slowing down the velocity in relation to an engine on gasoline (nor does the cylinder demand have to be greater).
Switching to alcohol will usually show even better increases in torque than horsepower.

Ken, your car doesn't disprove the theory. You are making better power on alcohol than gas, but would make more again if you optimised the runner volume for alky.
Also, depending on your combo, the extra tenth might be coming from an increase of torque only.
Alky makes more power because:-
It carries it's own oxygen.
It has good latent heat of evaporation properties.
It has higher calorific value at stoichiometric.

[maxracesoftware]

With the theory of "alky needs a larger port" I'm actually proving it wrong with the performance numbers, aren't I?

So what think Ye?

Ken

No.

like in my previous Post, you'll loose an immediate 8-12+ % PerCent Loss in Ve% just switching over to Methanol -vs- Gasoline,
..but you'll usually also pickup that same 8-10 % PerCent gain in Torque
with Methanol, even with the Ve loss

there's more HP/TQ waiting for you if you could recover more of that 8-12 Ve% Loss

further optimizing the Intake Port Runner cross-sectional area, port velocity, port shape for Methanol will get you even more TQ/HP gains, especially mid-range to top-end MPH/ET .

[Racer7088]

Could you extend this effect to other applications?

It would appear that the same sort of issue would crop up with turbocharged engines. As you improve the intercooling, (intake charge temp drops significantly) the ideal port size would need to be changed. Likewise folks running water injection or alcohol injection would by extension also need either more port size or perhaps slightly different cams to maximize the setup.

Does anyone have any observations on these related issues ?

Larry

Cams are way different due to the tremendously different pressure ratios ocurring when you run high boost especially with a smaller turbo. You can have MUCH more back pressure than boost pressure. You have to trim down overlap and/or open the intake later and close the exhaust earlier. There are some very knowledgable guys lurking here. i don't know if they will show themselves though as much work has been done to get where these guys are.

I CAN say that there are two weldtech heads really popular for 360 sprint car engines and one is the RP for Alcohol and one is the AP for gasoline and they are both 23 degree heads and both based on the 10X Brodix raised runner head and both are 230cc. The alcohol head has a smaller port and venturi and valve size but a larger and taller short turn and a smaller port entrance and also specs a smaller min intake cross section than the AP gasoline head.

This head, the RP, will pull out further in rpm as well than the higher flowing AP head will on acohol that also has a bigger valve and port because the short turn is just way too fast for the alcohol engines especially up nozzles to work with even though the gasoline engines make more power with that head than the RP. But again BOTH are right at 230cc so no big difference in port volume at all here.

[Racer7088]

Well, another question for ya.

If a typical gas engine needs multiple angles on the valve seats to keep fuel in suspension, does alky need more since there's a much larger volume of fuel involved? It was explained to me back several months ago that this was the reason for multi-angle seats rather than a radius type seat. I've heard that there are some shops that use as many as 7 different angles for some applications. Would this be something to look into with an alky seat? Or is it just so much fuel running thru the openings that it doesn't matter?

Ken

Maybe Larry maxracesoftware will know but I know that you probably could use a different valve job on some heads for sure.

[Jay Allen]

you just don't make the Int Port 10% Larger,
you have to Pitot Probe the Ports to find potential Choke areas.

Air Speed in Port areas when using Methanol -vs-Gasoline.
Example=> if the pushrod area is just perfect area/velocity FPS for Race Gas, then that same area will be a Choke when switching over to Methanol...you have to Slow-down the FPS...by making that area 10% larger

if you have a 260 CC Int Port (gasoline),..then its very possible that by the time you finish increasing the Port Areas to achieve the correct FPS to account for Methanol in Int Ports, then that same Int Port Volume will windup 10 % larger at approx = 286 CC's(Methanol)

the 10% Rule seems to work great with Craig Bourgeois 's A/ND Nostalgia front engine dragster
http://www.maxracesoftware.com/race_car_pictures.htm

another thing Erik mentioned is effects of Down-Nozzles,
however, its very possible that if Down-Nozzles point too much
spray towards the Short Turn, you will definetely loose some HP/TQ,
or at the least not show any real HP/TQ gains with Down-Nozzles -vs- Runner Nozzles.

Very good post Larry. As usual. Thanks for clearing things up.

And I agree that when down nozzles are being used, the intake port volume is not as important.

[hotrod]

Cams are way different due to the tremendously different pressure ratios ocurring when you run high boost especially with a smaller turbo.

Yes your right! You can have 2.5x boost pressure on a small turbo on the exhaust side.

The thing that caught my attention is how especially in the turbocharged import, Buick GN and the street supercharger cars, water and alcohol injection are becoming very popular again. Thinking along the lines of what Larry Meaux mentioned in his post. The drop in VE due to the change in mach number of the flow as it cools down should also apply to WI and AI. If you have a head that works great in a turbocharged application on gasoline with manifold air temps around 105 - 135 deg F or higher, and you start dumping 200 - 500 cc/min of methanol or water-methanol mix into the air stream, that air flow is suddenly going to drop in temp by some where in excess of 50 deg F.

You will be able to make more power with the WI or alcohol injection due to the high effective octane you get, but you may be leaving power on the table due to the drop in VE caused by the colder air charge and how it changes port flow characteristics.

In the case of the WRX, the stock heads are already too small for a performance application. They go into sonic choke around 6000 rpm on the 2.0 L block according to the formulas Larry Meaux has posted. WI will likely make the sonic choke a much more significant issue if my observation is correct. Its of interest to me right now, as I am currently shopping for ported heads for my car. Right now the two best options appear to be the Axis Power ported heads with the oversized valves and 8500 rpm kit and the new Cosworth CNC ported heads for the WRX. If I go with the Axis Power stage 4 block I'll definitely need more port area to feed the larger engine at higher rpms. Maybe Bill Jones has already addressed this on the Subaru heads he ports?

It seems to me, that if you want to get the max power out of WI, or alcohol injection on any engine which has high manifold air temps, without the injection, you need to consider this effect.

These heads and manifolds should require the same sort of port modifications, (slower air flow) used on alcohol engines. Obviously they also need to look at the wet flow characteristics of the manifold and heads as well.

I know folks port the nitrous applications differently, but in the case of WI I am not so sure anyone is considering this issue. At least I have not heard anyone discussing it.

Maybe this is obvious and common practice to the big league head shops, but it is an interesting consideration I had not thought much about before.

Larry

[Ron E]

Could you extend this effect to other applications?

It would appear that the same sort of issue would crop up with turbocharged engines. As you improve the intercooling, (intake charge temp drops significantly) the ideal port size would need to be changed. Likewise folks running water injection or alcohol injection would by extension also need either more port size or perhaps slightly different cams to maximize the setup.

Does anyone have any observations on these related issues ?

Larry

Cams are way different due to the tremendously different pressure ratios ocurring when you run high boost especially with a smaller turbo. You can have MUCH more back pressure than boost pressure. You have to trim down overlap and/or open the intake later and close the exhaust earlier. There are some very knowledgable guys lurking here. i don't know if they will show themselves though as much work has been done to get where these guys are.

I CAN say that there are two weldtech heads really popular for 360 sprint car engines and one is the RP for Alcohol and one is the AP for gasoline and they are both 23 degree heads and both based on the 10X Brodix raised runner head and both are 230cc. The alcohol head has a smaller port and venturi and valve size but a larger and taller short turn and a smaller port entrance and also specs a smaller min intake cross section than the AP gasoline head.

This head, the RP, will pull out further in rpm as well than the higher flowing AP head will on acohol that also has a bigger valve and port because the short turn is just way too fast for the alcohol engines especially up nozzles to work with even though the gasoline engines make more power with that head than the RP. But again BOTH are right at 230cc so no big difference in port volume at all here.

Eric
Having looked at them, do you think the alcohol-version of the 10X may have been due to their knowledge of alky needing more slow-down over the turn than gas, so, within the casting, they maxed out the turn area, and then, sized the valve and remainder of the port to this limitation?

Also, I’ve heard about it off and on for years, but is there an additive for Alcohol that makes the stuff visible in case of a fire?