For quit some time, I've been getting mail about where to really begin with
EFI.

So here's my notes, and opinions on things. Your results my vary some, but
there is alot of time spent in accumulating this info.. If you wan to
haggle over it, that's fine, but I'm probably not going to be the one to
haggle with. Unlike the talking heads that write magazine articles, every
item of info here is from actual testing, and analysing results. Some
explainations are simplistic, since this isn't a design course. What
matters is what works.

Mixing the fuel:
Fuel is made into a reactionable state thru atomization, and or
vaporization. The net result is the same, but manifolding and the type of
EFI to maximize the results differ greatly.

Atomization:
In this case the fuel is mechanically shredded, into fine particles.
It's how carburetors and TBIs (to a large extent) both work. In the TBI
it's just the venturis, and emulsions tube jobs that are replaced with
Injectors and electrons. The carb has the atomization taking place in the
venturi, and the TBI has it taking place at the edges of the Butterfly.
It works out exactly the same for WOT and MPG. The two advantages are cold
starts, and fuel sloush. Both have *wet* manifolds, and for that reason
are, usually hard to compare back to back, but using a Cross Fire lower
manifold and a custom lid for a Q Jet, the results were the same as far as
in the test car running mid 13s, and 27 MPG. The down side is at WOT the
fuel just flows past the butterfly, with min atomiziing. So at higher
speeds, you have to use some vaporization to keep the fuel in a suspended
state. If you relly look at some of the TBI manifolds they are very clever
in what the do. ie., on some they take the heater water out of the back of
the manifold, so in warmer weather the coolant flow thru the manifold for
the heater is min., so in the winter the manifold runs alot warmer. What
I did was run without a heater valve, so that there was always some coolant
running to help vaporize the fuel. In order to make it most uniform in
temp., I did block off oil reaching it, with a lifter valley pan. Also,
ran a 180dF thermostat. This allowed for the best combo of cold hot, high
low rpm drivibility. Everything has it's trade offs.
The wet manifold has some issues that you want to consider. There is an
optimum range for air speed thru it. Too slow and the fuel falls out of
suspension, and too high, and it *sticks* to all the runners, where they
bend. If the manifold had not enough heat, or wrong plenum volume you can
also wind up with the fuel traveling in rivers along the base of the plenum.
These details are not to be ignored. First, thing most guys think is that
more air cleaner is better. Nope, it can drop the air velocity down low
enough that the fuel is puddling, and not in a good state for reacting in the chamber.

Vaporization:
This is where heat is used to evaporate the fuel so that it can be reactable with air in the combustion chamber. On your TPI type systems the fuel is just sprayed on the back of the intake valve (well kinda sorta near it) and then just waits around boiling til the valve opens. SEFI can really help this process at idle and low rpm, but very low in the rpm range the advantage is lost. So for a real HiPo engine it can help, that's about the only reason for it. In the real world of new car sales, it does
matter since they are selling millions of cars and each lil bit helps with CAFE etc., but in our world you'll not likely see any big difference, till you get to the large injector area.
With the injectors close to the port the manifold is rather dry, so air speed tends to be more flexible, since fuel falling out of suspension isn't such a big deal. BUT, what can be an issue is the runner tuning, to cover the low speed problem of not enough heat to really boil the fuel. So the
engineers made the compromise of using the runner lenght to really enhance
the low speed cylinder filling.
Also, turbo really like this, since at serious boost levels the air temp is elevated and boils the fuel nicey (all things being relative).
There is a real problem with TPI and vaporization at high rpm. The
later LT1s, LS1s, have really a well designed system, and in all honesty are
far better then the earlier TPIs. But, again, the TPIs have a fairly nice series of ecms that can be tuned to min., their short comings.

Matching Components:
Contrary to lots of info., the only hot set up involves testing what your
engine likes. No dyno, or part that looks right means much when the green
flag drops. Testing, testing, testing. Do what the engine tells you it
likes. On some extensive testing, I found a 2.25x14 K+N to be faster then
a 3x, or 4x, and that was optimizing the fuel and timing to within 1%, and
1degree.
If you want ram air, there are two considerations, the volume of the
ducts, and the actual air intake. The ducts seem to work best at equalling
the engine displacement. For it to be real ram air the intake must extend
forward of the sheetmetal by several inches, or the scoop several inches
above the hood line. The Mopar Chassis Book has some good notes on this.
Just as an honorable is cowl induction. I will alow the engine
compartment to vent hot air when standing still, and the as speed raises,
force air into the engine compartment. You can run into some weird cooling
problems, if you soon't understand that the cowl induction is great at
filling the low pressure area under the hood, and that mins airflow thru the
radiator.
Also, remember, that all the airflow bench flow testing is done steady
state, and that just doesn't happen in the real world. Lil airfoils and
such might show a gain on a flow bench and do nothing for an actual engine.
And at some time or another there is reversion, which can be a good thing or
at least managed, that Never shows on a flow bench.

Operating temps.:
No reason for running less then 180, and personally I get best results
with 190dF. Thing most people ignore is oil temps., and that has alot to
do with the actual piston temp....... Some claim better resistance to
detonation, well I can run 3d more timing then peak HP, in my turbo car, and
we'll just say it runs quick. Using a low temp thermostat to control oil
temps to some degree just don't make sense to me.


General Conclusions:
In stock form,
TBI, is for the lower rpm range engines.
TPI, does about the same, but has slightly better metering.

Modified,
They both can do a really grand job if you maximise their strong points,
and min the weaker points.
TBI, you want to use a well thought out manifold. Single plane is best.
You need to run some controlled amount of manifold heat, for High RPM
useage, since you lose the atomization advantage there. No real need in
trying to run a TBI off of a TPI ecm, BTDT. You want the faster pulsing
rates to help with the atomization.
TPI, bigger plenums, shorter runners (or at lest shared runners). You
want textured runners for the increase in surface area. Since they are
basically dry you can get by with a smaller runner manifold for the same HP
level as a TBI.

Detonation:
It occurs in the chamber. First thing to work on is getting the chamber
right. Min., it surface area, and for heavens sake radius the chamber to
cylinder head surface edges, just .01" or so but you should be able to rub
yourfinger all around the chamber and not draw blood...
Want to run 11:1 CR?, Fine, just be sure to have a late closing intake
valve.
The less timing needed the better, 76cc heads WOT 36idh degrees, 64s
34ish, 56 AL 28ish. Again the less the total timing for a given level of
HP the better. Plug gap can reduce the amount needed to, just it's hard on
ignition components.

Thinking:
If it works it works, ain't no more difficult then that.
Reading plugs is necessary, period. Like it or not, they are the eyes
into the combustion chamber.
Experimenting without a base line is just wasting gas.
Be honest with yourself.
Do what you can afford to do.
Don't think cause something worked on your car that it's a universal
truth.
If you think your going get recalibrating a car right for the first time
in 100-200 chips, your just wishing aloud. There are a million combinations
for what may work.

 

Boy you were not kidding when you said that you have been spending some time doing a little writing

BW

Other topic, Glad your trip went well. it was a short one, so good news i take it.

------------------
Bobalos
aka Bob W.
www.r71camaro.homestead.com
r71chevy@earthlink.net
<><

 

Bravo, good work. That just answered and clarified alot of question's that i had even before i start getting into Prom Tuning. BTW, Anyone haveing trouble getting list emails from DIY-EFI? I haven't got any emails since this weekend.

------------------
89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Gutted cat
-!AIR
-Gutted Air Boxes

 

https://www.thirdgen.org/messgboard/...ML/001197.html

BW

 

Thanks for the insights Bruce. I always enjoy reading your posts.

 

There's been a few questions regarding tuning and I have been referring people to find this article. I just want to put it back to the top so people can easily find it and read it.

 

Be nice to set them off to the side somewhere, if that happens, please send the injector sizing one there.

Make ya a deal,
set those 2 off as a ***
and I'll do a final DFI vs GMECM, when and why, and a MAF vs MAP when and why.

Well, might be Doc Bashful and Sleepy to help

 

How have you been getting mail? You don't have your e-mail posted in your profile .
Anyways, excuse my slang but..."this is some good ****"
Definatly get all the useful eprom info onto a page somewhere.

------------------
, Jon (350 TBI!)
91 Red My website

 

I'll second that. Do you think we could get a FAQ page for this forum?

 

Great idea Bruce. There have been some great posts that I think would form a good DIY PROM FAQ.

 

JPrevost, I bet you have never read this article. Definitely good reading. http://www.geocities.com/MotorCity/S.../prog_101.html

 

"You want textured runners for the increase in surface area." ---TPI


Why do want the runners to be textured for the TPI? I thought that because they are "dry" you would want them to be smooth to reduce the boundary layer and increase flow potential? Why the increase in surface area? OR were you talking about TBI?


James

[This message has been edited by james_fearn (edited May 25, 2001).]

 

Somebody that knows more about airflow will have to explain why, but the best flow comes from a slightly rough surface. I've seen the actual flow bench test of the same heads polished and then roughened. The rough port produces less turbulence and more flow.

 

I won't get into the "theory" of why, but it probably has a lot to do with why a dimpled golf ball travels further than a smooth golf ball.

 

People tend to thnk of air as just a gas. Infact it acts just like water, just that it's about 1/600 as dense.

This is just for getting a mental picture of how air acts, and then you can draw your own conclusions.

Watch a large ship go thru the water, and how even with a sharp bow to cut thru the water builds up around the nose and then forms a wake. This is especially important for how the body goes thru air.

The air around the car is actually moving slower then the ground speed of the vehicle.

Now we can see that at various heights over a moving body, or air moving over something, the air speed changes.
With a slightly rough port, these layers aren't allowed to form up, and get as organized, so the faster moving air has a large diameter to move thru.

If you really want to get up to speed on the aero world, there are two big items super sonic, and subsonic, and they are totally differennt worlds. After reading some aircraft and rocket design books you can really see who in even F1 has done their homework. Specially if you read up on the stall regions of wings, aspect ratios, and dihedral, and cathedral wind design.

Like I mentioned above don't forget on the TPIs they are only sometimes dry flow.

I worked at a shop where we did porting, and people used to pay extra to slow their cars down for the polishing, I tell em all day long that it would cost em HP, and yet 99% of em wanted it done. Remember, the engine will tell you what works, it really is easy to tune, if you don't try to please yourself with what you're doing

 

Boy another class on fluid dynamics, & I thought i was done with that stuff when i left Nuke school . all's i want to do is to make my car faster than Joey up the street

BW

------------------
Bobalos
aka Bob W.
www.r71camaro.homestead.com
r71chevy@earthlink.net
<><

 

Ya, but Joey reads alot.....LOL

http://naca.larc.nasa.gov/reports/19...i?page0001.gif

 

Thanks Grumpy, I couldn't have said it better myself.
Let's hope others apreciate your efforts.

Don>>>

------------------
Chronologically challenged. But still kicking!
'92 CAMARO RS
305 TBI 5/spd (now TPI)
B4C Alt.
'69 camaro-BB/Lenco,1050 dominators, /Pump Gas/no drugs 8.97-150+/3200lbs.
SoCal Thirdgen F-Bodies

 

Grumpy,

What level of "roughness" are we talking about? I have been using 120 grit sanding rolls to smooth "finish" my runner & base, after using 80 grit to grind....



------------------
Mike Metzler (Desert86Roc)[*] Webmaster: SpeedWorldMotorplex.com[*] Click Here For 86 IROC 305 TPI (406 build in progress) Page

ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.365 @ 86.785 mph (uncorrected, headers, no NOS)
<><

 

Great reading.
There is a strong tendency in the Syclone/Typhoon group to push for lower temps at any cost. Heat is thought of as the enemy. IA temps in the sub 100 deg. range are prized. The thought is - the lower the temps - the denser the air - more fuel can be utilized - more power is generated.

This philosophy leads to 160 deg. thermostats, more efficient CCHE's and heat exchangers. The lower the better. It sounds like there should be a target somewhere in the middle to maximize and maintain atomization. Is there a low point at which detonation can not be lowered? What have you found to be an optimal IA temp.

Do you have any thoughts on this? Is there a compromise position that will deliver the best power with enhanced long term reliability?

------------------
George Betzhold
92 Z-28 Convertible
93 Typhoon #2115
86 S-10 flamed w/ 95 4.3 Vortec driveline

 

The 160dF thermostat is just old outdated info.. Period.

IAT has a great deal to do with the amount of timing you can run, and just a slight bit on fuel.

What folks often ignore is oil temp., and that has a huge effect on piston temp., You never want to let the oil temp get over 240dF.

If you read up on the Evans Cooling system stuff they go into great detail about how a cooling system actually works (not that I'm impressed with their system). ANyway, what you want to do is raise the boiling temp limit, IN THE CYLINDER HEAD. Meaning water pump speed, and outlet restriction.

There is a practical limit for cooling the intake charge, after that it's all about tuning, and that's where things get messed up.

I've seen one sy in particular start with 90dF IAT and finish the 1/4 at 115dF, and run 12s easily with a stock setup. On my GN up to 120s seems fine (but I was running alot more boost).

Remember some heat is a good thing for vaporization, which is what you want to capitialize on.

Course then we get to water injection, and all the falicies that go with it. Water is both a fuel, and oxidizer. But, folks just blindly go on about detonation suppression, and ignore what's really going on.

I'm not too sure about the last 2 years fuel brews (from the refineries), but it used to be the lower end boiling temps., were about 130-150dF. So if your IAT are 120 or less I'd say you OK, and just work on the other stuff I mentioned.

 

Another good read.