Yes, thank goodness for moderators.

 

Where's Waldo?



what's wrong w this picture?

given the fact we are on page 28 of this thread which i will re-name a couple of years on the dyno you might not remember that my first run on the rollers in Nov 10 ended w a general loss of comrpession.... which later was diagnosed as a broken primary injector diffuse that went thru the motor.

o k, must have been cracked... weird as we don't see much of that. refresh the motor and away we go.

fast forward to Jan 16 2012.

another disappearing diffuser.

there are no coincidences. and after arriving home and hopping in the shower where i get my ideas the light bulb clicked on.

Luke and i shared quite a bit of time today going over the data and looking at the ports for AFR readings. prior to seeing the diffuser that was not there Luke after a complete review of the data said that there was absolutely nothing amiss other than a final tune.

i had been thinking that we may have had a flow difference between the front and rear secondary injectors...

the ports are exactly the same color so toss that idea.

Luke mentioned that no way could we have knock w the amount (2500 CC) of meth going into the motor. (and the Datalogit confirms no unusual knock) he said he felt that the charge air temp was zero F. placing your hand on the UIM supports that.

no knock no broken motor.

back to the shower... the diffusers are some form of plastic. i know as i had to remove their melted remains from the Nov 2010 incident.

plastic at below zero. ever heard of wind chill?

what is the temp at zero ambient at 500 MPH? the charge in the ports at full blast (bad pun) is moving into the engine at around that speed. when the port closes Newton's Third Law is operative and the charge bounces back to the throttle plate before heading again towards the motor. so we have a spindly piece of plastic easily at sub zero temps being buffeted by huge dynamic force. (Luke is thinking anodised aluminum diffusers if a diffuser is necessary) opinions/advice welcome

lest you think that this sounds weird as you haven't lost a diffuser consider the relative cooling of methanol and gasoline...

Gasoline 952 cooling BTUs per gallon

Methanol 3136 cooling BTUs per gallon

and yes water has alot more at 8087

BUT

you aren't using much water... 500 CC?

i am using 2500 CCs of meth at the motor/diffuser failure point.

AND

water does not atomise (cool) hardly at all in the runners. it does it's job in the combustion chamber well past the diffuser.

i have run meth since 2004 and have extensively dynoed w it w no diffuser problems... until 2010. for the 2010 trubo comparo project i swapped my two 700 (each) solenoids for two 1000 CC solenoids.

more meth... bye bye diffuser.

the motor comes apart this weekend. i will need a rotor and rotor housing. the turbo gets checked at BR and will be rebuilt if the slightest damage exists to the turbine wheel. the bearing is perfect and the turbine wheel looks perfect from the outside but the inside may be a different story.

if it is in rebuild i will simply swap in the Garrett 3574 which is next in line.

of course i need to prove out the chilled diffuser theory and then come up w a fix.

any advice welcome.

i am breathing easier tonight as the only thing worse than a broken motor is a broken motor w no ideas as to the why.

i also am breathing easier because there was NO reason for the motor to fail based on all the logged data.

we move on.

howard

 

Wow never would have thought of that

 

 

I get to spend a few days each winter in places like Edmonton and Thunder bay. When the temp get's down to -30C or so plastic pieces on my luggage and things start breaking. That the diffuser would break in those conditions doesn't surprise me at all! Impressed you thought it through. Sounds completely logical to me.

 

Definitely interested in whatever fix you come up with. I broke one once when pulling it out of the housing. I would pay to not have to worry about that ever again.

 

Interesting

 

Mmmm carbon fiber diffuser anyone?

 

doesn't matter what they are made out of, they still don't cure detonation.

 

I've always cut the bottom portion of the diffuser out, basically just using the top sealing portion. Never had an issue with idle quality etc..

 

True; but they should be more thermally stable and vibration resistant.

 

Can't wait for the next round of results. GL Howard.

 

here are a couple of pics of what was left of my front primary diffuser. i think my situation is probably somewhat unique in that most are not running straight methanol (with pump as base fuel) and those that might be are probably not running 2500 to 3300 CCs...

i do believe that those that are running lots of meth have probably removed their diffusers. i talked to my go to guy re them and he said... he was surprised that i had them in my motor. he runs 14 1600 injectors, that's not a typo, with meth as a fuel. i asked him what he thought the charge air temp going into my motor w 2500 CC of meth and he said "easily below freezing."

but what does he know.. he only makes more than 1100 rwhp from his 2 rotor, runs in the mid 7s w his 2000 pound RX3 and was speaking to me from the infield of Daytona where one of his engines was getting ready to qualify for the Rolex.

so let's use 32 degrees. now we add in airflow speed to figure wind chill. let's be conservative and figure 300 mph. how much heat would be drained from these plastic diffusers? and we are talking about an airflow saturated w alcohol. think how cold your skin feels when you rub it w alcohol. now add more alcohol and 300 mph...

anyway, here's what they look like. i am no materials expert but the ragged surface of the breakaway looks like a basic material failure.

the probable cause for the two failures is the methanol. that's why most generally don't have diffuser failures.

 

Hmm.. I'm thinking i'll be either removing them completely and replacing mine with alum ones or shaving mine down completely to eliminate the actual diffusor parts. Good to know...facts are facts.. thanks for the R & D Howard

 

Sorry to see your troubles Howard. At this point most guys with modified fuel systems are using top feed injectors with the aluminum sleeves so have deleted those guys altogether. If we do have customers still using them (ex with side feed 850/1300s and BNR twins) then we always specify brand new OEM replacement parts. Looks like in your case new wouldn't have mattered.

Btw, there's a lot of trash talking in this thread and complete lack of respect by some armchair quarterbacks. We're all in this community to make it better guys, not sure why all the negativity. If you don't like what's going on in this thread, you're free to steer clear of it

 

For what its worth, during these cold months up north here with too much meth injection you will see ice form on the outside of a carburetor. This was even back in the days of not using an intercooler(70s)...

 

"even back in the days of not using an intercooler"

it might be interesting for some to know that my 1100 hp drag racer friend does NOT run an intercooler. the methanol delivers the knock out cooling punch even at 1100 hp allowing him to not have any boost restriction from the IC or the weight...

BTW, it was the rear diffuser that failed in 2010. my egts are normally less than 30 degrees apart indicating even flow distribution.... partially due to the ground zero LIM.

hc

 

what is this "front primary diffuser"?

 

wind chill isnt the correct way to think about it. That is a sensation experienced by your nerves on your skin. The wind moves molecules across your skin at a high rate which lowers your skins temperature faster. Its doesn't make it any colder.

The venturi effect causes a temperature decrease due to a decrease in pressure. This is brought about by the increase in velocity of air from a narrowing opening. Essentially Bernoulli's principle and the equation of continuity interacting.

Then comes that matter of thermal conductivity. Plastic is astoundingly low for K values (about 0.2) as compared to say steel at 50 or aluminum at around 230. The higher the number, the more thermally conductive it is.

The plastic used on your luggage, i can promise you isnt the same compound. If anything heat appears to be the greater enemy for these things, unless your injecting liquid nitrogen.


More over, why the heck would would retain these silly things if they have broken before? I have had my S4 13b in my 82 eat two of these things thus far. The only way i knew was changing manifold gaskets when transferring the engine (its been in a few cars) and it has never killed it. The second time, i stopped putting them whole and just use the top part.

 

One of HUNDREDS of burning/common sense questions that come to mind when reading this thread. And I wouldn't be surprised if it gets deleted. If it doesn't I'll be sure to use your post as a template for asking questions!!

 

^ Agree. Most likely not a necessary part; especially considering the cars main purpose (Texas standing mile).
Saying that. What affect would their elimination really have? Micro change in gas mileage?

 

I removed my primary diffusers for a bit in an S4 TII engine.. it caused hesitation during cruise and it idled rougher. I put them back in, problems went away. my guess is without them, the fuel just shoots straight across and hits the opposite wall instead of atomizing properly

 

someone please skool me on what a diffuser is and what it's suppose to do. my engine has never been opened up and run great and i'd like to keep it that way. i would rather delete it and not ruin a pristine engine. what's needed?

side question but i feel is still relavent.... reliably, how much power can a 13b put down without meth? unlike people in the quad digit hp range i will have an FMIC.

 

both diffusers broke in my first turbo 13b and took out both rotors. i wont touch them now

 

nsk1, go back and look at the picture in post 677 and you'll see the diffuser in the left port. The diffuser is a plastic piece under the primary injectors that helps spread out, diffuse, the fuel spray from the injector into the air flow. You don't want to tear your motor apart to remove them!