Intake mods and simple math. Those calculators must not be so great!!!
02-12-2009, 09:24 AM
#61
Le Mans Master
From Vader's website:
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What fuel pressure setting will give me the best performance?
A: The stock setting is 42 PSI. Much track testing has showed that any type of increase will greatly benefit both horse power and torque. Here's some dyno testing on a stock 350 motor which substantiates those claims:
42 PSI (stock) 46 PSI 50 PSI
RPM Torq HP Torq/diff HP/diff Torq/diff HP/diff
------------------------------------------------------------------------
2250 237.7 101.8 254.9/17.2 109.2/ 7.4 275.0/37.3 117.8/16.0
2500 241.7 115.1 262.1/20.4 124.8/ 9.7 283.3/41.6 134.9/19.8
2750 241.5 126.5 275.2/33.7 144.1/17.6 297.0/55.5 155.5/29.0
3000 237.1 135.4 278.2/41.1 158.9/23.5 305.5/68.4 174.5/39.1
3250 233.8 144.7 278.9/45.1 172.6/27.9 311.3/77.5 192.6/47.9
3500 241.0 160.6 278.2/37.2 185.4/24.8 309.5/68.5 206.3/45.7
3750 246.6 176.1 283.4/36.8 202.4/26.8 303.3/56.7 216.6/40.5
4000 250.4 190.7 278.3/27.9 212.0/21.3 298.0/47.6 227.0/36.3
4250 251.6 203.6 272.5/20.9 220.5/16.9 289.1/37.5 233.9/30.3
4500 253.5 217.2 257.3/ 4.2 220.5/ 3.3 277.0/23.5 237.3/20.1
4750 245.0 221.6 242.1/-2.9 219.0/-2.6 266.4/21.4 240.9/19.3
5000 227.6 216.7 225.0/-1.4 214.2/-2.5 237.8/10.2 226.4/ 9.7
It shows that by increasing the fuel pressure to 50 PSI, results in maximum torque increase of 58 ft-lbs (along with a much flatter torque curve) and a maximum horse power increase of 19 HP over stock. 46 PSI also provides a noticable increase which should work well for day-to-day street driving. An adjustable fuel pressure regulator (see Chap 5.2) is required to increase the fuel pressure.
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Saaaaweeet!!! I like it!! But, wait... Look at Plemon's website:
======================================== ============
Adjustable Fuel Pressure Regulator - One of my personal favorites on the useless items list is the adjustable fuel pressure regulator. The concept behind this modification is pretty sad. The claim on this mod is that by increasing the fuel pressure you can effectively tune your engine to take advantage of your other modifications. The problem with this theory is that such changes are global, meaning that if you increase the fuel pressure you will make your injectors flow more fuel at every given point in the RPM band. This might work if your A/F ratio is globally lean or globally rich, but I can tell you from experience that this is rarely the case. At part throttle the increase in fuel pressure will make the injectors flow more fuel than they were intended to. The computer will see this as a rich condition as detected by the O2 sensors but it will not know why. The computer will reduce the injector pulse width to compensate, this messes up the fuel trim tables and in the case of the Corvette fools the computer into thinking it is getting better gas mileage than it really is. This modification makes the computer have to constantly adjust the fuel trims which is not a good idea. For best performance the computer needs to know exactly what is going on, it should not be fooled. As long as an engine is running stock fuel injectors and is not running nitrous or forced induction there is no reason to ever mess with the fuel pressure. If a modification requires serious changes to the A/F ratio these changes need to be done in the computer to be truly effective. You might correct your A/F ratio at one RPM with the adjustable fuel pressure regulator but in the process mess it up in another part. This is a terribly inaccurate way to tune a car.
======================================== ===========
Note the part I highlighted....
Now, I never thought of Nathan as a guy to spout BS, but the numbers above don't seem to lie either. Sure, the numbers on top are for a L98, but the operating principles of the two aren't that different.
======================================== ============
What fuel pressure setting will give me the best performance?
A: The stock setting is 42 PSI. Much track testing has showed that any type of increase will greatly benefit both horse power and torque. Here's some dyno testing on a stock 350 motor which substantiates those claims:
42 PSI (stock) 46 PSI 50 PSI
RPM Torq HP Torq/diff HP/diff Torq/diff HP/diff
------------------------------------------------------------------------
2250 237.7 101.8 254.9/17.2 109.2/ 7.4 275.0/37.3 117.8/16.0
2500 241.7 115.1 262.1/20.4 124.8/ 9.7 283.3/41.6 134.9/19.8
2750 241.5 126.5 275.2/33.7 144.1/17.6 297.0/55.5 155.5/29.0
3000 237.1 135.4 278.2/41.1 158.9/23.5 305.5/68.4 174.5/39.1
3250 233.8 144.7 278.9/45.1 172.6/27.9 311.3/77.5 192.6/47.9
3500 241.0 160.6 278.2/37.2 185.4/24.8 309.5/68.5 206.3/45.7
3750 246.6 176.1 283.4/36.8 202.4/26.8 303.3/56.7 216.6/40.5
4000 250.4 190.7 278.3/27.9 212.0/21.3 298.0/47.6 227.0/36.3
4250 251.6 203.6 272.5/20.9 220.5/16.9 289.1/37.5 233.9/30.3
4500 253.5 217.2 257.3/ 4.2 220.5/ 3.3 277.0/23.5 237.3/20.1
4750 245.0 221.6 242.1/-2.9 219.0/-2.6 266.4/21.4 240.9/19.3
5000 227.6 216.7 225.0/-1.4 214.2/-2.5 237.8/10.2 226.4/ 9.7
It shows that by increasing the fuel pressure to 50 PSI, results in maximum torque increase of 58 ft-lbs (along with a much flatter torque curve) and a maximum horse power increase of 19 HP over stock. 46 PSI also provides a noticable increase which should work well for day-to-day street driving. An adjustable fuel pressure regulator (see Chap 5.2) is required to increase the fuel pressure.
======================================== ============
Saaaaweeet!!! I like it!! But, wait... Look at Plemon's website:
======================================== ============
Adjustable Fuel Pressure Regulator - One of my personal favorites on the useless items list is the adjustable fuel pressure regulator. The concept behind this modification is pretty sad. The claim on this mod is that by increasing the fuel pressure you can effectively tune your engine to take advantage of your other modifications. The problem with this theory is that such changes are global, meaning that if you increase the fuel pressure you will make your injectors flow more fuel at every given point in the RPM band. This might work if your A/F ratio is globally lean or globally rich, but I can tell you from experience that this is rarely the case. At part throttle the increase in fuel pressure will make the injectors flow more fuel than they were intended to. The computer will see this as a rich condition as detected by the O2 sensors but it will not know why. The computer will reduce the injector pulse width to compensate, this messes up the fuel trim tables and in the case of the Corvette fools the computer into thinking it is getting better gas mileage than it really is. This modification makes the computer have to constantly adjust the fuel trims which is not a good idea. For best performance the computer needs to know exactly what is going on, it should not be fooled. As long as an engine is running stock fuel injectors and is not running nitrous or forced induction there is no reason to ever mess with the fuel pressure. If a modification requires serious changes to the A/F ratio these changes need to be done in the computer to be truly effective. You might correct your A/F ratio at one RPM with the adjustable fuel pressure regulator but in the process mess it up in another part. This is a terribly inaccurate way to tune a car.
======================================== ===========
Note the part I highlighted....
Now, I never thought of Nathan as a guy to spout BS, but the numbers above don't seem to lie either. Sure, the numbers on top are for a L98, but the operating principles of the two aren't that different.
Never mind this info was at the bottom of page 1 not page 4....old info.
Last edited by engle1147; 02-12-2009 at 10:19 AM. Reason: Never mind this was the bottom of page 1 not page 4.
02-12-2009, 12:02 PM
#62
Race Director
Thread Starter
Wow... That's an old post! 
After what I've read/learned in the past year, the idea of having pressure boosted just a hair above what's "needed" doesn't seem that bad. IOW, if you need 42psi for your injector size/config, a 44 psi setting might provide a nice boost for WOT operation.
Otherwise, getting the computer tuned to where it needs to be is the route that makes most sense.
Another interesting thing I saw recently (but don't remember where) is that our fuel rails are lower than 42/43 psi. Two posts in a row said they were @ 39 psi (nominal) -- which if I'm not mistaken is where Ford rails are at.
I meant to post about this because I assumed the place where I saw/read it must be wrong.
After what I've read/learned in the past year, the idea of having pressure boosted just a hair above what's "needed" doesn't seem that bad. IOW, if you need 42psi for your injector size/config, a 44 psi setting might provide a nice boost for WOT operation.
Otherwise, getting the computer tuned to where it needs to be is the route that makes most sense.
Another interesting thing I saw recently (but don't remember where) is that our fuel rails are lower than 42/43 psi. Two posts in a row said they were @ 39 psi (nominal) -- which if I'm not mistaken is where Ford rails are at.
I meant to post about this because I assumed the place where I saw/read it must be wrong.
02-12-2009, 12:16 PM
#63
Le Mans Master
I think what is going on is that "ford" injectors are rated for their flow at the advertised rate at a 39 #age...maybe those guy are trying to match the flow rates by dropping the pressure @ the rail. Or they might be running larger than stock injectors and have to drop the rail pressure to compensate for the "over" flowage. Don't know.
haven't seen this for while
02-12-2009, 12:55 PM
#65
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Otherwise, getting the computer tuned to where it needs to be is the route that makes most sense.
What happens here is that when the throttle position sensor goes to WOT position the ECM sets the BLM cell # to 15 which has a permanent trim value of 128, the ECM also sets the INT trim value to 128. With both trim values set to 128 the ECM does NOT trim A/F even though it still shows closed-loop mode on the scanner.
Further the injector flow rate change goes as the SQRT of the fuel pressure change, so increasing fuel pressure from 44psi to 48psi resulted in ~5% increase in flow...at WOT only. Of course when not at WOT the ECM must trim off injector pulse duration to maintain stoch A/F, so the MPG readout will be in error.
[now back to the 76cmf argument]
I've just been thinking about your reasoning that 76cfm is adequate air flow for the engine you sized. Though that is true, remember that the intake valve open duration in time is shorter as RPM increases. Therefore you need runner & head flow much greater than 76cfm.
This explains (qualitatively) why, when the #113 heads are properly ported, valve size increased and a multi-angle valve job done, one can reasonably expect to see in the order of a 30chp gain in power.
BTW, another "trick" suggested for our TPI plenum is to flute the plenum openings down into the upper runner flanges. The idea is that as the dynamic air is suddenly drawn down into a stock runner it must make a 90deg turn; since air has mass, at hi velocities it tends to overshoot the opening edge thus effectively reducing the runner diameter. Fluting this opening allows air to flow in more smoothly, rather like the way air flows sloothly out of a musical horn for maximum effect & volume.
BTW, though I run a 52mm TB, descreened MAF, have ported the plenum intake and fluted the openings, none of these mods showed up as HP gains on my time slips.
02-12-2009, 01:05 PM
#66
Race Director
Thread Starter
I think what is going on is that "ford" injectors are rated for their flow at the advertised rate at a 39 #age...maybe those guy are trying to match the flow rates by dropping the pressure @ the rail. Or they might be running larger than stock injectors and have to drop the rail pressure to compensate for the "over" flowage. Don't know.
02-12-2009, 01:18 PM
#67
Race Director
Thread Starter
[now back to the 76cmf argument]
I've just been thinking about your reasoning that 76cfm is adequate air flow for the engine you sized. Though that is true, remember that the intake valve open duration in time is shorter as RPM increases. Therefore you need runner & head flow much greater than 76cfm.
This explains (qualitatively) why, when the #113 heads are properly ported, valve size increased and a multi-angle valve job done, one can reasonably expect to see in the order of a 30chp gain in power.
I've just been thinking about your reasoning that 76cfm is adequate air flow for the engine you sized. Though that is true, remember that the intake valve open duration in time is shorter as RPM increases. Therefore you need runner & head flow much greater than 76cfm.
This explains (qualitatively) why, when the #113 heads are properly ported, valve size increased and a multi-angle valve job done, one can reasonably expect to see in the order of a 30chp gain in power.
In simplest terms, you only have 1 of the 4-stroke engine cycles to get air in the cylinder (e.g., the intake stroke). So, 76cfm / 1/4th = 304cfm. If the motor had 100% VE, then you could make the case that 300cfm is what heads needed to flow.
In EA Pro engine simulations I've seen, 350ci motors show quite a bit more potential using a 280cfm head vs a 260cfm head. (Most of the improvement is in the 5k-6k rpm range mind you.) Those same simulations show a 350 hitting -- and exceeding 100% VE near harmonics of the intake/headers/etc....
So, having 280cfm heads doesn't sound like the overkill I thought it would be back -- at the time this thread was originally posted. Of course, my change in thinking is why I have a set of AFR 195's in my basement now!
gp
12-17-2010, 02:34 PM
#68
Indeed there is a point were modifying the ECM's fuel trim tables is needed. However, when my L98 was building close to 300chp (1st dyno chart) I was running near 48psi with stock injectors and my scanner showed the O2 sensor value of close to 920mV at WOT which correlated with the 12.5:1 A/F from the dyno pull chart.
What happens here is that when the throttle position sensor goes to WOT position the ECM sets the BLM cell # to 15 which has a permanent trim value of 128, the ECM also sets the INT trim value to 128. With both trim values set to 128 the ECM does NOT trim A/F even though it still shows closed-loop mode on the scanner.
Further the injector flow rate change goes as the SQRT of the fuel pressure change, so increasing fuel pressure from 44psi to 48psi resulted in ~5% increase in flow...at WOT only. Of course when not at WOT the ECM must trim off injector pulse duration to maintain stoch A/F, so the MPG readout will be in error.
[now back to the 76cmf argument]
I've just been thinking about your reasoning that 76cfm is adequate air flow for the engine you sized. Though that is true, remember that the intake valve open duration in time is shorter as RPM increases. Therefore you need runner & head flow much greater than 76cfm.
This explains (qualitatively) why, when the #113 heads are properly ported, valve size increased and a multi-angle valve job done, one can reasonably expect to see in the order of a 30chp gain in power.
BTW, another "trick" suggested for our TPI plenum is to flute the plenum openings down into the upper runner flanges. The idea is that as the dynamic air is suddenly drawn down into a stock runner it must make a 90deg turn; since air has mass, at hi velocities it tends to overshoot the opening edge thus effectively reducing the runner diameter. Fluting this opening allows air to flow in more smoothly, rather like the way air flows sloothly out of a musical horn for maximum effect & volume.
BTW, though I run a 52mm TB, descreened MAF, have ported the plenum intake and fluted the openings, none of these mods showed up as HP gains on my time slips.
What happens here is that when the throttle position sensor goes to WOT position the ECM sets the BLM cell # to 15 which has a permanent trim value of 128, the ECM also sets the INT trim value to 128. With both trim values set to 128 the ECM does NOT trim A/F even though it still shows closed-loop mode on the scanner.
Further the injector flow rate change goes as the SQRT of the fuel pressure change, so increasing fuel pressure from 44psi to 48psi resulted in ~5% increase in flow...at WOT only. Of course when not at WOT the ECM must trim off injector pulse duration to maintain stoch A/F, so the MPG readout will be in error.
[now back to the 76cmf argument]
I've just been thinking about your reasoning that 76cfm is adequate air flow for the engine you sized. Though that is true, remember that the intake valve open duration in time is shorter as RPM increases. Therefore you need runner & head flow much greater than 76cfm.
This explains (qualitatively) why, when the #113 heads are properly ported, valve size increased and a multi-angle valve job done, one can reasonably expect to see in the order of a 30chp gain in power.
BTW, another "trick" suggested for our TPI plenum is to flute the plenum openings down into the upper runner flanges. The idea is that as the dynamic air is suddenly drawn down into a stock runner it must make a 90deg turn; since air has mass, at hi velocities it tends to overshoot the opening edge thus effectively reducing the runner diameter. Fluting this opening allows air to flow in more smoothly, rather like the way air flows sloothly out of a musical horn for maximum effect & volume.
BTW, though I run a 52mm TB, descreened MAF, have ported the plenum intake and fluted the openings, none of these mods showed up as HP gains on my time slips.
12-17-2010, 08:19 PM
#69
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now point out what the restrictor plate 2bbl does to the motor off the corner???
could it be...it doesn't respond as well... ie... revs slower...
so maybe more cfm is about!! how fast it can accelerate the air to the max cfm!!! which equates to higher ve at relativly lower rpms and carries this higher ve through the rpm range.... its like you can only suck in 607cfm into your lungs... now do you want to pull it through a 607 cfm straw (1/4") dia or a 1500 cfm pipe (1 1/2" Pvc)...?
12-17-2010, 09:12 PM
#70
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A) Do you have a point or question?
B) You can post a link to an older thread (or thread post) w/o dredging up the post. With your new post, make your point and reference the old one as needed. But, then again, where's your point here?
C) The L98 is a "torque machine" primarily due to it's intake. Beyond that, it's the nature of a V8 vs fewer cylinders. Convert the intake -- which you are allowed to do and a V8 can become a revving motor. Leave the intake on and you'll never pull thru 6k -- with any kind of power.
D) WTF?
B) You can post a link to an older thread (or thread post) w/o dredging up the post. With your new post, make your point and reference the old one as needed. But, then again, where's your point here?
C) The L98 is a "torque machine" primarily due to it's intake. Beyond that, it's the nature of a V8 vs fewer cylinders. Convert the intake -- which you are allowed to do and a V8 can become a revving motor. Leave the intake on and you'll never pull thru 6k -- with any kind of power.
D) WTF?
Looks like his point was to say thank you.
12-18-2010, 09:56 AM
#72
Melting Slicks
Here is a basic example of what's tickin me off....
48mm TB is big enough -- even for a modded motor and a factory 502. 4 cycle motors turn twice to fire. At 6000 rpms, a 350CID motor requires 607cfm. That means a 48mm TB at 650CFM is big enough. Fine....
48mm TB is big enough -- even for a modded motor and a factory 502. 4 cycle motors turn twice to fire. At 6000 rpms, a 350CID motor requires 607cfm. That means a 48mm TB at 650CFM is big enough. Fine....
12-18-2010, 12:01 PM
#73
Race Director
Thread Starter
You are missing a very simple concept. Air flow figures are generally quoted at 28 inches of water pressure. That is 2.06 inches of mercury and a pressure differential that is unacceptable in any racing engine. They want to be closer to atmospheric pressure 5 inches of water or less. That same 200 cfm runner at 28 inches only flows 85 cfm at 5 inches of water. The reason they are fowed at 28 inches of water is to get a more accurate repeatable reading and to get the airspeed closer to what it will be in the engine.
Also, don't "miss" the fact this thread is 3yrs old. My personal questions were answered a long time ago!
12-19-2010, 10:18 AM
#75
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Well, Greg this is proof positive things CAN be brought back from the DEAD.....
If CFI-EFI could dig out of his snow covered cabin in Utah, and reconnect his land line , it would be complete?
Since you have a running motor @ 383 cu in with Siamese runners, cam, et al... how about an update on how it's doing?
AND do you see a lean condition in the back cylinders??
Haven't seen evidence of that on mine.
TJM
If CFI-EFI could dig out of his snow covered cabin in Utah, and reconnect his land line , it would be complete?
Since you have a running motor @ 383 cu in with Siamese runners, cam, et al... how about an update on how it's doing?
AND do you see a lean condition in the back cylinders??
Haven't seen evidence of that on mine.
TJM
12-19-2010, 04:05 PM
#76
Melting Slicks
If you're going to change topics and try to qualify engine flows on a 5 inch of water scale, why not (re)explain how that relates to head flows that are given in 28" of water?
Also, don't "miss" the fact this thread is 3yrs old. My personal questions were answered a long time ago!
Also, don't "miss" the fact this thread is 3yrs old. My personal questions were answered a long time ago!
Dave
12-19-2010, 07:31 PM
#77
If you're going to change topics and try to qualify engine flows on a 5 inch of water scale, why not (re)explain how that relates to head flows that are given in 28" of water?
Also, don't "miss" the fact this thread is 3yrs old. My personal questions were answered a long time ago!
Also, don't "miss" the fact this thread is 3yrs old. My personal questions were answered a long time ago!
12-19-2010, 10:55 PM
#78
Race Director
Thread Starter
I am delighted you have neen elightened and will do my very best to never answer a thread you have started on whatever the subject. Perhaps you could suggest the time limit to bring up a previous thead that will not cause you upset or distress as that is not how we should be acting here. I am sure you know this but will remind you e-mail and forums with threads are flat expressionless conversations with no feel as to what the person is saying and no way to know if they are smiling frowning scolding or just being a moron in general. I will start a new thread on air density vs. cfm so as not to interfere with your previous gained conclusions.. fair enough..
Dave
Dave
Sometimes I get cute when people aren't following forum guidelines. The one I'm thinking of now is the "45-day rule".
Originally Posted by Corv08Vette for the CF
If an existing thread has not received a reply for a period of 45 days or more, members should create a new thread which is identical or similar in nature, rather than to post to the existing one.
Similar or identical threads created under 45 days will be considered a dupe, and will be locked accordingly.
This rule will not apply to technical discussions or to posts in threads where such posts have been made to update the threads with information deemed by moderators to be of benefit to Forum members.
Similar or identical threads created under 45 days will be considered a dupe, and will be locked accordingly.
This rule will not apply to technical discussions or to posts in threads where such posts have been made to update the threads with information deemed by moderators to be of benefit to Forum members.
Rest assured, people frequently buy/use parts that don't benefit their overall goals.I hope someone does add meaningful information/explanation to this thread. The one thing I ended up doing (after learning from this thread) was picking the best flowing heads (in my price-range) though using a modest cam. The combination allowed me to get BOTH the flow AND the torque I wanted for my goals. It's a concept people rarely seem to consider since most people start grunting like "Tim, the toolman Taylor" when they're talking about builds. That's when caution can out the window.
Best I can say at this point -- is my 383 runs quite well. The valve train seems a bit noisy but I may be able to "fix" that. Torque is just dog nuts. Pedal response (off-idle) is rediculously good. My powerband landed right where I wanted it. I can LEAP around town and pull HARD with a simple shift to 4th on the hwy. (3rd if below 60mph). Torque is exciting all the way from idle to 5k rpms. It will, of course go beyond that. But, my mega-ported SLP intake did provide extra rpm ceiling. I can also get good mileage on the hwy (28ish). I may run on a dyno or for time later on. For now, I'm more interested in finishing the details. Too cold to do much now though. (My ECM is still hanging on the PS floor!) Plus, I started a new contract job.
Last edited by GREGGPENN; 12-20-2010 at 02:55 AM.
12-20-2010, 07:58 AM
#79
Melting Slicks
I was unaware of a 45 day rule and responding to a thread with recent posts. Personally I do not have the time to read every message in a thread in great detail and skim them quickly to see if a sensible answer has been posted well sensible in my experience anyway. I glanced at your original post and some suggested solutions and skipped to the end to post mine. Without blowing my own horn too long I will just mention I have been in the cylinder head and intake manifold design business for about 3 decades. A lot of companies have copied my original designs that i did as one off a very long time ago the Stealth Ram comes to mind right off the bat. I was doing those in the early80's and orginally designed for about 450 flywheel hp limit and had a larger manifold based on a Holley tunnel ram for more serious efforts. I will say the plenum I used was a much better design though much more expensive to build. The problem with all of them is price point and number of buyers that will pay what it really takes to have the best is very small. If anyone is interested in starting a thread about air flow pumping losses and that sort of thing please post and advise it if should be a new thread or add to this one.
Dave
Dave
12-20-2010, 10:25 AM
#80
Race Director
I've always thought that rule was silly for tech threads. It's typical to see threads started on the same subjects but they never go in depth. I'd rather see one big thread keep getting refined than many new threads with fluff for content.