Milwaukee Midget

[fordboy628]

This is more or less a duplication of the latest post on my Racing Engines 101 thread with some additional thoughts added . . . .

Here is a bit of free advice as my Holiday gift to everybody who reads the midget's diary.

Since I get asked this on a fairly frequent basis, this is how I typically approach an analysis of an unknown engine:    (say like maybe a Rover K . . . .  )

1) I run a geometry study for the engine as built, or as you want to build it, to reveal whether there is a "geometry" (typically rod length/stroke ratio) "issue". Poor geometry can affect the "flow demand", by advancing/retarding the point of maximum flow demand a few degrees, say 75/76 degrees ATDC Vs. 80/81 degrees ATDC. Unless your cylinder heads have "exceptional" low lift flow (doubtful on any two valve engine, especially with restricted valve sizes) this will negatively affect cylinder "filling/pumping" with the net result of a low volumetric efficiency and possibly a low bmep.   Knowing the "flow demand" for the displacement, rpm range and V/E is critical to "useful" planning

2) I then flow the cylinder head(s) with inlet and exhaust adaptors by themselves. I collect the data with a software program to eliminate "optimistic" eyeball values & hand entry. I then also flow test with the manifold attached, with a radiused adaptor. I then add the carb/whatever to the manifold and flow test the complete inlet tract. I know this is a lot of flow testing, but it also ISOLATES components so that any "issues" can be "identified". Knowing the flow test results for the complete inlet tract allows you to calculate two important pieces of information:

a) Does the inlet system flow enough to fulfill the required flow demand at the V/E and rpm the engine needs, or is being designed for?
b) The total inlet flow allows you to "predict" the peak bhp using SuperFlow's well published formula, INDEPENDENT of any other simulation software.

3) I then run the cam (or cams) profile with cam data logging software, although this can be done by hand, if it is done carefully. You can then "combine" the cam/valve lift profile with the inlet flow data to get "net valve flow data". This can be extremely useful, in my opinion, to evaluate differing cam grinds. It is also useful to know things other than the net valve lift curve, such as:

a) cam/valve velocity
b) cam/valve acceleration (not by hand)
c) cam/valve jerk rate (not by hand)

Most older, "vintage" engines have "packaging" limitations for valve train components, and it is helpful to know this ahead of time.  BEFORE selecting some "killer cam" that breaks valve train components on a regular basis . . . . .

4) Once you have collected the basic data/info, THEN, you can formulate a plan to improve output, based on sound engineering Vs. limitations/rules/costs.

Calculate your bmep @ your peak torque rpm. Well developed N/A engines should make 195/205 psi.    185/190 psi is my minimum bmep for respectability as a professional.
Very well developed N/A engines can achieve 225/227 psi!! But this is in professional racing with multi-million dollar budgets for development and research . . . . .

As you have already guessed, I spend a lot of time on analysis, either via spreadsheet or with proprietary commercial software written for the industry. One word of warning though. "Good" software to perform analyses is expensive, $500.00 and upwards . . . . AND, that is just the first issue, if the "analyzer" has little internal combustion experience.

BTW, it may be difficult to accumulate some of this data for your "oddball" little jewel, based on its' "oddity".   But you knew that already, didn't you?   Just fabricate your own airflow adaptors from mdf sealed with varnish or lacquer.    No whining allowed . . . . . .  just do it.

It is also important to point out that when increasing an engine's output, costs rise at an exponential rate to returns. Sometimes raising the bhp output significantly REQUIRES commitment to a "system" of componentry that is a "cascading nightmare of costs".   As in titanium valve train for example.   In a non-professional racing situation, ONLY the end user (the check writer) can determine if the expense is justified.   But you knew that already too.

And also, these are some examples of the type of additional analysis I've performed on a couple of threads besides the ones on the Milwaukee Midget's Build Diary:
A)  Australian Belly Tank/SOS Build Diary, reply #3648:                  http://www.landracing.com/forum/index.php/topic,862.3645.html
B)  XXO/BVGC '38 Chevy Coupe Build Diary, reply # 1497:              http://www.landracing.com/forum/index.php/topic,8271.1485.html

These types of spreadsheet analyses can be easily done to provide extra engineering "insight" into your special little jewel . . . . .

OK, this is the point where you now get to gather some data about what you are doing.   Then you get to put on your thinking caps, grab your calculator or sliderule and figure out where you can eke out some advantage or benefit for your particular powerplant, the way you are building it.

Keep in mind that data gathering and analysis can reveal some serious problems with a given build spec.   The big issue seems to be that most of the time: "ignorance is bliss". When you don't KNOW the maximum load on a part, or the maximum acceleration forces applied to assemblies, everything is "great", right?   Knowing this information ahead of time can prevent poor choices of development path and/or poor part selection choices . . .

Information, in and of itself, is neither "good" or "bad". My experience is: that once you start making information based decisions, you will also want to stop guessing about any engine related decisions . . . . JMHO.

And before I finish, I just want to make a comment about decision making. I have witnessed a few types of decision making in my career, I rate them in the following fashion:

1/ Information based decisions = * * * * *
2/ Science/info based guess = * * *
3/ Experience based guess = * *
4/ Letting your supplier decide what they "think" you need = *
5/ Wild a$$ guess = ?
6/ Hope for the best = ? ?
7/ Dartboard decision = ? ? ?
8/ Checking chicken entrails @ midnight = ? ? ? ?
9/ Other "Voodoo" or "magic" based choices = ? ? ? ? ?

The bottom line ALWAYS ends up being:  Your engine, your wallet, you get to decide . . . . .   CHOOSE WISELY . . . . .   


Just a few additional steps in the preparation process, seems simple enough, don't you think?   

Although you are on your own for devices that supply additional "brain cooling".    I recommend tasty, fermented and chilled beverages and/or a beanie copter cap.   

Best regards of the season to all, and
 
Fordboy

[Freud]

fordboy628, You are amazing.

You could also depress anyone without a plan for

building their engine. But if they have been planning

to go to Bonneville since 1975 engine details aren't

relevant anyhow.

FREUD

[Peter Jack]

Fordboy, you just explained exactly why I prefer to build chassis and have someone else with the knowledge and experience supply the engine for projects I get involved with. 

Pete

[Milwaukee Midget]

fordboy628, You are amazing.

You could also depress anyone without a plan for

building their engine. But if they have been planning

to go to Bonneville since 1975 engine details aren't

relevant anyhow.

FREUD

Here's what I learned from this - so far -

To an average hot rodder with a Jegs or Summit catalog, a subscription to Hot Rod and friends who drag race or oval track - it appears easy to bolt together that 700 horse small block or order up a crate engine and go racing.

Then reality sets in.

How many build diaries and pronouncements have we seen where they were going to put together a car and race, and 3 months into the project, all they've wound up with is a car with the fenders removed, an expired fire suppression system they bought on eBay for $20.00, a cast-off 9" and a wife screaming about the state of the garage?

Metaphorically, I could have wound up in that boat.

While I've acknowledged a lot of people who have helped me to this point, I will, right now, post up a copy of THE ONE ARTICLE that kept this project going, and continues to be a guiding light.

It's on page 7 of this PDF.  It was written by Peter Egan.

The minute after I read it, I said to myself - "I am not going to be that guy".

I think every racer should read this.

http://www.elcc.org/archive_newsletter/1986/LotusLines_1986_SepOct.pdf

[manta22]

That's a good article, Chris.

I read a book somewhere that said that pubs are full of people who decry the high cost of racing... with a cigarette in one hand and a pint in the other.

Regards, Neil  Tucson, AZ

[Dr Goggles]

"I wished I'd had the time to play in a band"

I wish I'd had a dollar for every time I'd heard that and another dollar for every time I'd restrained myself from making a smart -crack.
If I had those dollars I likely would have thrown them after the ones I've spent racing

The truth is, I had all the time in the world to play in a band, and I had nothing better to spend the money I've spent on racing ...maybe there were more important things, but those pursuits meant a lot to me and sitting around eating dry crackers so my superannuation was getting filled would be like being in prison...............

[manta22]

"I wished I'd had the time to play in a band"

I wish I had been able to play in a band but I was limited by my handicap-- no talent.

Regards, Neil  Tucson, AZ

[Interested Observer]

Fordboy,
A few questions about the Holiday Gift treatise..
1)  What is your definition of “flow demand”?
2)  On what basis is a new BMEP determined due to a proposed change in compression ratio?
3)  Despite a fairly thorough examination of the SuperFlow website, the “well published formula” for horsepower remained undiscovered.  Could you please provide more guidance?
4)  It has been my understanding that flow bench data is generated at a fixed pressure differential.  If that is the case, how do you generate realistic inlet cycle flow rates vs. valve position for varying cylinder pressures?  Are flow coefficients found for each valve position?  Seems like there would be a circular dependence between cylinder pressure during the cycle and the flow rate.  Is this resolved using an iterative process?

[Tman]

Very good article Chris.

[Milwaukee Midget]

Been an interesting few weeks since the holidays.  I’m still waiting on Mark to get his computer functioning properly – I was able to rib him a bit on that yesterday face to face, as I traversed the polar landscape that is the Cheddar Curtain this time of year.  

I won’t be naming names on this, but I have been permitted access to the inner sanctum of one of Fordboy’s compatriots.  This is as close to a living museum of vintage Brit tin (and fiberglass) as I’ve ever been permitted access.  After mopping up the drool off of the floor, I grabbed my trusty new Christmas Nikon (Thanks, Kate – still the best, that girl) and snapped off some photographic evidence of my foray into Wonderland –

Say what you will about Colin Chapman’s propensity to build understructured cars, the Élan is clearly one of the most beautiful sports cars ever to hit the track –



They even look good when stacked like cordwood on pallet racking . . .



Or stuffed in a corner . . .



I didn’t feel like climbing the ladder to the loft where the rest of them were stashed.

Minis?  Easiest way to turn a two car garage into a four car garage I can think of . . .

I’m particularly fond of the panel delivery . . .
                








Due to vertigo, I didn’t get a shot of the TR-6 hanging from the rafters, and the Capri 2600 was stuffed away in a place where I couldn’t get a clean shot, but the Cortina was just beyond cool . . .



But this was the reason for my visit.  Essentially an aluminum and carbon fiber clone of a works MGC – sitting right on the cusp of street car and racer –





And if that’s not quick enough – probably the most tastefully prepped MGB GT V8 on the planet –


THIS is how carburetion is supposed to be done . . .




 

[manta22]

Chris,

Were you blindfolded and led on snowshoes to this undisclosed location?

Regards, Neil  Tucson, AZ

[Milwaukee Midget]

Chris,

Were you blindfolded and led on snowshoes to this undisclosed location?

Regards, Neil  Tucson, AZ

Worse than that, and definitely more confusing.

Mark navigated.   

[Rex Schimmer]

Just shows the British love of tractor motors!!

Neat cars!

Rex

[Tman]

Crazy cool!

[tauruck]

I see Chris mentioned a Capri.

My first car at 18 was a South African version built by Basil Green called a Perana.
He shoehorned a Ford 302 into the Capri and the rest as they say is history.
If you wanted to learn drifting and cadence braking this was your car.

English body, American motor, South African driver= Weapon of mass destruction.