Fuel injectors & fuel pressure for best atomization, MPG and low to mid RPM power?

[Newold1]

Adam, thank you for straightening me out on this. I did not quite understand your goals here and now seeing the actual new TPI intake I can see and tell that it is more than capable of delivering more air than the original TPI intake even if it were modified. Nice Piece!

Being that you are using a Holley EFI ecm I am guessing that you are also connected with dual O2 sensors and air fuel ratios in closed loop are being adjusted based on the tune in the ecm. AS long as the ecm tune for the engine is adjusting the idle, part throttle and cruise air fuel ratios it should be possible to maximize the idle quality, a smooth acceleration and an best economy cruise conditions. The ultimate TUNE on this efi system will determine how well you achieve your best results. A chassis dyno tune when reprogramming will be a great tool.

I don't think any of the newer Bosch or Siemens injectors should have any problems meeting these goals provided the size of the injectors is nicely matched to the engine and horsepower and the fuel pressures are kept in the 43-45psi range they are normally rated at. Most of these newer injectors are mutli-orfice spray patterns that atomize and provide a nice degree pattern and a fine fuel spray delivery.

The issues you may experience in making the engine have smooth fuel efficient street manners will in my opinion come from the actual aggressive camshaft that you are using. The 110 LSA that you are indicating will lower manifold vacuum at 650-750 rpm range and a smooth idle quality and low rpm acceleration will not be optimum for the street and cruising. Most street mannered EFI SBC's are factory equipped with LSA's in the 112-116 degree range and some newer engines actually get LSA up near 119 degrees.

This is a contention area that shows up in over mild engine builds where the owner "want's his cake and eat it too" You might want to decide which is more important, the nice 440HP engine build result or the smooth high efficiency mpg and docile low rpm street manners then cam and tune accordingly.
Compromise might ultimately find a happy medium. JMHO

[NewbVetteGuy]

The issues you may experience in making the engine have smooth fuel efficient street manners will in my opinion come from the actual aggressive camshaft that you are using. The 110 LSA that you are indicating will lower manifold vacuum at 650-750 rpm range and a smooth idle quality and low rpm acceleration will not be optimum for the street and cruising.

The cam LSA was definitely a tradeoff geared towards power vs. fuel efficiency, I admit. I gave Mike Jones every minute detail on my build (including 355 rear gears, 2,500 RPM TC stall, & 4L60e with torquey, low 1st gear) and my goals and out of the magic Jones algorithm came my cam. He did explicitly mention that since I was going with aftermarket EFI that I could get by with the 110 LSA and the statement hinted that an OEM computer wouldn't like it. I have the utmost confidence in the cam.


Adam

[1989TransAm]

On my highly modified TPI intake Mike Jones cut my camshaft at 233/233 and the lift virtually the same as yours with 1.6 rocker arms. LSA was @ 113 to help pass California smog. However I have 369 cubes. We flowed the First intake manifold itself with no runners attached and I believe port 2 was around 290 cfm. We did make up a bell inlet to the port so it would flow decently. There is a lot of information over on thirdgen.org. I have never messed with the First runners themselves.

[turbo2256b]

EGR is still the best answer for fuel economy in a set up like the OPs

[MadBill]

Especially if the manifold has no provision for EGR, a lean cruise island (perhaps as lean as 17:1 in its center) in the spark and fuel tables will do pretty much the same for F.E. with less tuning effort.

[NewbVetteGuy]

On my highly modified TPI intake Mike Jones cut my camshaft at 233/233 and the lift virtually the same as yours with 1.6 rocker arms. LSA was @ 113 to help pass California smog. However I have 369 cubes. We flowed the First intake manifold itself with no runners attached and I believe port 2 was around 290 cfm. We did make up a bell inlet to the port so it would flow decently. There is a lot of information over on thirdgen.org. I have never messed with the First runners themselves.

Yep. Sorry I mis-spoke on the worst flowing runner. The average was still just over 300cfm if I remember correctly, right?

I think your cam is likely based upon Jones's HR73353 profile (if I understand correctly he customizes the LSA and exhaust duration based upon the data that gets submitted in the form); mine is a HR70375 profile on the 110 LSA with 230 exhaust duration. http://jonescams.com/hydraulic-roller-tappet/


This cam was specced for the build that you did with the aftermarket runners siamesed down pretty far, right? -If so the bigger duration on your intake side makes sense to me as I'd expect your HP peak to come later with the shorter total runner length.

BadSS from the ThirdGen forums fired up EA Pro for me, using the information that he had already put into the tool for his personal build and then modified it based upon my heads, exhaust, and cam, for what that's worth. He estimated the hp peak @ 5,800 RPM with it carrying flat to 6,200 - 6,300 RPM. -That's essentially what Mike Jones said when he speced the cam, too. To me the flat area from 5,800 - 6,200 means that airflow / intake length tuning has hit it's max and the cam intake duration is slightly over-speced vs. the runner's desired hp peak to hold the HP peak a bit longer instead of it falling off a cliff. -Have any thoughts on this, 1989TransAm?

1989TransAm: Any idea whether the FIRST runner would support any Siamesing? (I think I remember people having to get them welded up a bit more first.) -I'm afraid that in the future if I rebuild the bottom-end to a 383 that my peak HP RPM is going to move down even further and to move it back up to around 6,200, I'd certainly consider siamesing at that time.


On the bell inlet, I vaguely remember this from a thread on Thirdgen; what tool did you end up using for this and did you use it on all runner inlets to increase the strength of the intake ramming effect or just on the weak runners to try to even the airflow & AFR out cylinder to cylinder? How much difference do you feel that this actually makes?


Adam

[NewbVetteGuy]

EGR is still the best answer for fuel economy in a set up like the OPs

I know and I'm REALLY kicking myself for not buying headers with provisions for EGR... The headers and 4L60e trans were the first two things I bought...



Adam

[NewbVetteGuy]

Especially if the manifold has no provision for EGR, a lean cruise island (perhaps as lean as 17:1 in its center) in the spark and fuel tables will do pretty much the same for F.E. with less tuning effort.

You really think so?!? (That would make me feel less bad for not knowing to buy headers with EGR provisions, given my mpg goals.) I definitely am worried about detonation with a 10:1 static CR, a small-ish cam and a long runner intake cramming that much more air into the cylinders.

When tuning for cruise RPM max fuel economy, at a certain point if I lean it out too much, it'll start pinging as soon as I hit a hill or outside air temp goes up 20-30 degrees F. Am I better off to richen up the AFR or to drop the ignition timing? (My guess would be to fatten up the AFR and leave the ignition timing alone.)


Adam

[1989TransAm]

The bell inlet for the intake was custom made for flowing TPI style manifolds. It had a slot for the mounting bolt and used one of the existing bolt holes to attach to. I would say 300 cfm is about right for the average flow numbers. I think the highest port we got was around 308 cfm.

The camshaft sounds good for your goals and your 350. I had the AFR 195 Competition heads which flow a little better than the regular AFR 195 heads.

I did port one of the First intake manifolds. You have to be careful on port 2 as you can get into the water. The main goal was to get the right cross sectional area and taper. Also to straighten out the port as much as possible. I think we did some welding in certain areas. Port 7 dips down quickly to clear the distributor. I think we welded reworked that area to straighten it out more.

As to the runners, yes people have welded them up and siamesed the upper portion of the runners in order to reduce the length from a harmonic standpoint. I will try to find my chasis dyno and post it for you.

[1989TransAm]

I was able to find one of the chasis dyno charts. This is with a highly modified long tube runner TPI that flows around 320 cfm. Jones Camshaft 233/233 with a 113 LSA. Holds on pretty good to 6600 rpm. The dyno operator was getting nervous as most of these cars do not operate at this high of an rpm and he shut it down. I would have like to have seen it go to 7000 rpm but it was a dyno day and people were waiting to put their car on the dyno.

I don't think we locked up the 3600 rpm stall converter in those days and that is why the dyno run starts at around 4000 rpm. Later on I went to a Yank 4000 stall and got the 11.57 run at 116 mph. No reason your First cannot do that but it would take some work and not out of the box unless things have changed. I know the guy selling these was making small changes. I have just not kept up with it.

Dyno 32611 Run 24.JPG

[MadBill]

Especially if the manifold has no provision for EGR, a lean cruise island (perhaps as lean as 17:1 in its center) in the spark and fuel tables will do pretty much the same for F.E. with less tuning effort.

You really think so?!? (That would make me feel less bad for not knowing to buy headers with EGR provisions, given my mpg goals.) I definitely am worried about detonation with a 10:1 static CR, a small-ish cam and a long runner intake cramming that much more air into the cylinders.

When tuning for cruise RPM max fuel economy, at a certain point if I lean it out too much, it'll start pinging as soon as I hit a hill or outside air temp goes up 20-30 degrees F. Am I better off to richen up the AFR or to drop the ignition timing? (My guess would be to fatten up the AFR and leave the ignition timing alone.)


Adam

At light loads, say 50-60 MPH level cruise with a non-brick-like vehicle, I've always been able to lean out a carb to the point of lean surge (usually ~ 16:1 or so) together with more advance.
Forty years ago one of GM's leaders called the occasional slight light throttle ping of many then-current models "The sound of Economy."
It takes time to dial in the optimum mix of spark and fuel for all the cells in the relevant tables and blending the cruise zone into the surrounding higher load regions.

[1989TransAm]

Bill, there is a "cruise" mode in the TPI software. I know we activated it when tuning by car. Under a light load the AFR is around 16:1 or so.

[MadBill]

Ah, that would probably get you 95% of the possible fuel economy with 5% of the effort! Back in the early nineties I was trading LeSabres yearly and from one year to the next, I lost 3-4 MPG on the highway when the regulations forced GM to delete the lean cruise mode. (It ran at 16.5:1)

[mk e]

Especially if the manifold has no provision for EGR, a lean cruise island (perhaps as lean as 17:1 in its center) in the spark and fuel tables will do pretty much the same for F.E. with less tuning effort.

You really think so?!? (That would make me feel less bad for not knowing to buy headers with EGR provisions, given my mpg goals.) I definitely am worried about detonation with a 10:1 static CR, a small-ish cam and a long runner intake cramming that much more air into the cylinders.

When tuning for cruise RPM max fuel economy, at a certain point if I lean it out too much, it'll start pinging as soon as I hit a hill or outside air temp goes up 20-30 degrees F. Am I better off to richen up the AFR or to drop the ignition timing? (My guess would be to fatten up the AFR and leave the ignition timing alone.)


Adam

A friend of mine has a 1966 Pontiac pic 6 , i think its over 10:1 cr...anyway it has been running over 20:1 since like 1974 and over 25:1 since he did an efi conversion in the mid or late 80s. It gets 33 mpg last I knew, up from low 20s stock.

The timing is up to something like 55 degrees at cruise, it surged otherwise. I knew he does the timing using egt....he looks for the lowest number.

I think oems got away from lean burn due to high nox? But for sure vacuum decreases the effective cr and the engine efficient along with it. That is the main point of all the turbos popping up....cruise with the turbo off and the throttle near wide open where the engine is most efficient, then spool the turbo when the drivers wants more power.

[NewbVetteGuy]

Ah, that would probably get you 95% of the possible fuel economy with 5% of the effort! Back in the early nineties I was trading LeSabres yearly and from one year to the next, I lost 3-4 MPG on the highway when the regulations forced GM to delete the lean cruise mode. (It ran at 16.5:1)

MadBill, I think I like you! Probably because you're telling me exactly what I want to hear, but I can admit that; lol!

95% the fuel economy for 5% the effort sounds wonderful. 16:1 - 16.6:1 AFR lean cruise mode for me, then.


Adam