Larry's Soft Head

hydra · Post by **hydra** » Sun Apr 23, 2006 2:52 am

Larry,
Nice to see you on here...
I'm sure you've been a lot of places and tried a lot of things in your day, nothing you said justifies some of the more "extreme" claims you've made. I realize you have absolutely no obligation to do so, but could you please produce some cold hard evidence to back up your claims?

Diesel engines run higher compression ratios and leaner A/F ratios than even you can dream of, and they don't achieve the economy figures you claim...
Modern state of the art GDI engines (the kind you don't get in the US) can also run A/F ratios on the order of 40:1, and they're not even in the same ballpark either...

I'm not constipated in my thoughts or ideas, and neither am I unwilling to see the "light". Show me something resembling conclusive evidence and I will gladly shut up and eat humble pie

Cobra · Post by **Cobra** » Sun Apr 23, 2006 10:56 am

Thank you Larry for groundbreaking advances in racing technology! Your place in racing is set in history!

hydra · Post by **hydra** » Sun Apr 23, 2006 11:42 am

For those of you who are interested here is some more info on the Fireball head:

http://www.eng-tips.com/viewthread.cfm?qid=63761

http://www.eng-tips.com/viewthread.cfm?qid=35479
Near the bottom of the page...

Note that Marquis is a Jaguar Powertrain Development Engineer so I would imagine he knows his stuff...

Ape · Post by **Ape** » Sun Apr 23, 2006 12:12 pm

Hurrah,
finally the sae paper number on the VW passat study, thank you very much for that valuable link.

papers written by Michael May (I. Mech. E. C204/79 & C97/79 + SAE 790386 / 1979) taken of the named page.

cheers + thank you

hydra · Post by **hydra** » Sun Apr 23, 2006 12:16 pm

Ape,
You've got PM!

Farrell · Post by **Farrell** » Sun Apr 23, 2006 2:27 pm

Hey gang, it's cool that after 20 years Larry has still got people talking. While I don't normally read Hot Rod I bought the issue with the Endyn story. Not because of it, but because it was the first time I had been to Bonneville, and there was coverage of it. As a 23 year old with a flow bench the talk here got me thinking about mixture conditioning for the first time. Six years later I was involved with an SCCA Pro Atlantic Cosworth Bdd that just happened to use a short deck Lotus block, shorter con rods, bigger than normal intake ports and a welded up clover leaf chamber. It had 15.5:1 static compression and ran happily @ .420 and would still make power @ .380. The definition of the term transient response became really apparent. Ex temps were down in the 1100's. The Cosworth intake ports have about a 5 degree divergent angle and we always biased the flow to the cylinder wall side so the flow fronts would, presumeably, meet in the middle and cause swirl. The only down side to all the ratio in the motor is that the cooling could not be compromised during a race. The funny thing about the enduring Endyn controvery is tha it reminds me of my older brother whom is a musician and known for calling down bands he'll hear on the radio. I just say "they might suck, but they're somewhere talking about you". Larry made me think, and think out of the box, which I still continue to do. Thanks Larry

automotive breath · Post by **automotive breath** » Sun Apr 23, 2006 3:20 pm

Farrell wrote:....ran happily @ .420 and would still make power @ .380. The definition of the term transient response became really apparent. Ex temps were down in the 1100's. ...

Farrell, can you provide advice on running a soft head engine with ultra lean air/fuel ratios. What conditions should be avoided, what to watch out for?

Farrell · Post by **Farrell** » Sun Apr 23, 2006 5:53 pm

Well Mr Breath, I can't claim any particular insight or knowledge of ultra lean burn combustion, it was a side benefit of the architecture of this one project 16-17 years ago. Two things really stand out to me, though. First is the second law of thermodynamics, convection, has to be utilized. Hot goes to cold not the other way around. Second is that homogenization not stratification of the air fuel mixture is essential. Earlier in the post there was talk of the May chamber. I remembered it from the time I had to do a valve job on our '64 Chev walk in van with a 235 in it. I saw it again when I worked for a guy that built Mercedes Benz motors. 25 years later I'm trying to achieve this in high boost diesel engines by directing charge motion from the exhaust side of the chamber to the inlet side. Unlike gas though, diesel doesn't like a rapid combustion. The resultant pressure spike is not a kind thing. Even with injection pressure in the 25000 to 30000 psi range the atomization will never be what it is with gas. Wether this is a latent heat of vaporization or surface tension thing, I don't know. I'll tell you this much though, when a guy wants to go fast with a late model 6BT Cummins, off comes the electronics and on goes the P pump. And when they run they are black smokin' pigs all the way down the strip. Hmm, kind of like a top fuel car. Just trade fuel vapor and flames for smoke. As a side note, we recently did the head, pump and installed a larger set of twins on a customers drag truck, speaking of longer burn cycles, and now I'll be darned if doesn't bend push rods. I've trying to get the cam grinder to retard the exhaust lobe and possibly shorten it up. Back to the Endyn thing for a sec. I'm inspired by good questions not easy answers. Thanx Larry

putztastics · Post by **putztastics** » Sun Apr 23, 2006 8:31 pm

Farrell wrote:I'll tell you this much though, when a guy wants to go fast with a late model 6BT Cummins, off comes the electronics and on goes the P pump. And when they run they are black smokin' pigs all the way down the strip. Hmm, kind of like a top fuel car. Just trade fuel vapor and flames for smoke. As a side note, we recently did the head, pump and installed a larger set of twins on a customers drag truck, speaking of longer burn cycles, and now I'll be darned if doesn't bend push rods. I've trying to get the cam grinder to retard the exhaust lobe and possibly shorten it up. Back to the Endyn thing for a sec. I'm inspired by good questions not easy answers. Thanx Larry

Do you know a Comp461 in the diesel drag world?

automotive breath · Post by **automotive breath** » Sun Apr 23, 2006 8:55 pm

Farrell wrote:...Two things really stand out to me
First is the second law of thermodynamics, convection, has to be utilized.

Second is that homogenization not stratification of the air fuel mixture is essential.

Thanks Farrell,
I’m particularly interested in combustion temperatures with a homogenized ultra lean air/fuel mixture. Is there a point that the mixture gets so lean that combustion temperatures decline?

putztastics · Post by **putztastics** » Sun Apr 23, 2006 9:18 pm

homogenization

Ok why not do what Smokey (and others) have done, totally vaporize the fuel before it gets to the chamber with intake heat higher than the end point of vaporation for gasoline?? Seems simpler than the soft head way of increasing fuel vaporization efficiency.

What we might be talking about is an increase in vaporization efficiency, if vaporization efficiency (before the chamber) is 100% then we are not running liquid fuel through the chamber and cylinder.

The same thing could possibly be accomplished by superheating fuel well over its end point of vaporization and under pressure injecting then with EFI, the fuel would flash to vapor. (Might be something to try with diesel...)

Is there any sort of catalyst that would increase the efficiency of vaporization?

How about platinum on the front end and burning the "unburned hydrocarbons" in the chamber instead of the converter or before a turbo at the least? Should get something out of burning the "unburned hydrocarbons" instead of just wasted heat.

automotive breath · Post by **automotive breath** » Sun Apr 23, 2006 10:16 pm

putztastics wrote:... totally vaporize the fuel before it gets to the chamber with intake heat higher than the end point of vaporation for gasoline?? Seems simpler than the soft head way of increasing fuel vaporization efficiency....

Adding heat to vaporize fuel has it's advantages and disadvantages. Work is done by expansion of the mixture, therefore a cooler mixture has a the potential to do more work than the same mixture with more heat.

If total fuel vaporization can be accomplished with out adding heat to the process the benefits will surpass vaporizing the fuel with heat.

cencodsm · Post by **cencodsm** » Mon Apr 24, 2006 12:12 am

automotive breath wrote:Is there a point that the mixture gets so lean that combustion temperatures decline?

Yes, in order to satisfy laws of conservation, there is a peak flame temperature.

Play with this for a while:

http://www.wiley.com/college/mechs/ferg ... flame.html

Equivalence ratio is just the inverse of lamda.

E=actual AFR / Stoichiometric AFR

automotive breath · Post by **automotive breath** » Mon Apr 24, 2006 1:06 pm

cencodsm wrote:Yes, in order to satisfy laws of conservation, there is a peak flame temperature....

Thanks cencodsm, this is exactly what I’m looking for!

lil289 · Post by **lil289** » Thu Apr 27, 2006 1:17 am

Larry, if you're still out there... or anyone else who may have some experience with this...

Someday, when I have the budget and the space, I want to experiment with some of the soft head ideas. I don't think I can to the whole custom piston thing with the one-sided dome but I just wanted to experiment with you're special intake valve seat design. I know from reading your articles that you deliberately kill low lift flow on the intake side. Do you compensate for this by running more duration on the intake side? If so how much more? Can you tighten up on the LSA too? How much? What range of lift is affected by your seat design? 0-.200"?

Thanks Larry