Ignition targets
10-24-2018, 05:27 PM
#46
Pro
I would say that the stock S62 runners you are running at the moment are too long for top end power, if this is what you are after.
It's not hard for me to imagine that shorter runners of equal length will give better top end breathing than the bizarre stock intake with its unequal length runners.
The firing order shows that the 4 "short" (or same side) runners (5/4/8/1) are being fed alternatively to the 4 "long" (or opposite side) runners (3/7/2/6).
This means the charge effect is not optimised to work best either at low/mid range (with 8 equal length "long" runners) or at high rpm (with 8 equal length "short" runners), and that's without even mentioning load losses due to bends. If the flappy, when open, is supposed to improve charge effect at low load, it's no going to help at all at upper rpm because the runners remain too long, and probably the reason why it is programmed to close at 5k rpm on a stock engine.
Sorry if this is not the right thread to discuss it, but what do experienced 928ers think about it?
It's not hard for me to imagine that shorter runners of equal length will give better top end breathing than the bizarre stock intake with its unequal length runners.
The firing order shows that the 4 "short" (or same side) runners (5/4/8/1) are being fed alternatively to the 4 "long" (or opposite side) runners (3/7/2/6).
This means the charge effect is not optimised to work best either at low/mid range (with 8 equal length "long" runners) or at high rpm (with 8 equal length "short" runners), and that's without even mentioning load losses due to bends. If the flappy, when open, is supposed to improve charge effect at low load, it's no going to help at all at upper rpm because the runners remain too long, and probably the reason why it is programmed to close at 5k rpm on a stock engine.
Sorry if this is not the right thread to discuss it, but what do experienced 928ers think about it?
10-25-2018, 01:28 AM
#47
Drifting
I would say that the stock S62 runners you are running at the moment are too long for top end power, if this is what you are after.
It's not hard for me to imagine that shorter runners of equal length will give better top end breathing than the bizarre stock intake with its unequal length runners.
The firing order shows that the 4 "short" (or same side) runners (5/4/8/1) are being fed alternatively to the 4 "long" (or opposite side) runners (3/7/2/6).
This means the charge effect is not optimised to work best either at low/mid range (with 8 equal length "long" runners) or at high rpm (with 8 equal length "short" runners), and that's without even mentioning load losses due to bends. If the flappy, when open, is supposed to improve charge effect at low load, it's no going to help at all at upper rpm because the runners remain too long, and probably the reason why it is programmed to close at 5k rpm on a stock engine.
Sorry if this is not the right thread to discuss it, but what do experienced 928ers think about it?
It's not hard for me to imagine that shorter runners of equal length will give better top end breathing than the bizarre stock intake with its unequal length runners.
The firing order shows that the 4 "short" (or same side) runners (5/4/8/1) are being fed alternatively to the 4 "long" (or opposite side) runners (3/7/2/6).
This means the charge effect is not optimised to work best either at low/mid range (with 8 equal length "long" runners) or at high rpm (with 8 equal length "short" runners), and that's without even mentioning load losses due to bends. If the flappy, when open, is supposed to improve charge effect at low load, it's no going to help at all at upper rpm because the runners remain too long, and probably the reason why it is programmed to close at 5k rpm on a stock engine.
Sorry if this is not the right thread to discuss it, but what do experienced 928ers think about it?
Given the engine's displacement, compression ratio, cam profile, intended usage of the vehicle, etc, specifically, what should the runner length, slope, and inside diameter be?
10-25-2018, 06:18 AM
#48
While one may be able to dimension a runner to perform best for a given engine speed (all other components being equal) it still won't give one the real world feedback of how trying different runner sizes impacts the performance of their particular engine, and trial and error is not only the proper way to learn but also the proper way to get an actual feel of what's going on with one's particular engine when adjusting a single variable. This is more satisfying and brings results more quickly than understanding but possibly getting lost in the mathematical description of the actual dynamic behaviour, in my opinion and experience. I have read quite a few posts in the archives where some knowledgeable folks seem to drown into interesting and accurate but perhaps excessively theoretical considerations without having actually tried to modify the intake for the sake of testing and comparing their results with the theory.
drnick's S62 runners are "too long" in the same way that S4 runners are "too long" - they were not designed to maximise higher rpm cylinder-filling, which is of interest for a minority of people who prefer to drive an engine that is more powerful and more responsive on the throttle at higher rpm than a high production number standard engine designed as a compromise to safely satisfy the masses, i.e. to make sales.
Still, I do not understand the cylinder-filling sequence of the S3/S4 intake which alternates between 4 "short" runners and 4 "long" runners. The flappy introduced on the S4 intake closes at 5000 rpm most likely to limit the Helmholtz effect which will be counterproductive at higher engine speed due to the "too long" runners.
drnick's S62 runners are "too long" in the same way that S4 runners are "too long" - they were not designed to maximise higher rpm cylinder-filling, which is of interest for a minority of people who prefer to drive an engine that is more powerful and more responsive on the throttle at higher rpm than a high production number standard engine designed as a compromise to safely satisfy the masses, i.e. to make sales.
Still, I do not understand the cylinder-filling sequence of the S3/S4 intake which alternates between 4 "short" runners and 4 "long" runners. The flappy introduced on the S4 intake closes at 5000 rpm most likely to limit the Helmholtz effect which will be counterproductive at higher engine speed due to the "too long" runners.
10-25-2018, 11:16 AM
#49
Drifting
While one may be able to dimension a runner to perform best for a given engine speed (all other components being equal) it still won't give one the real world feedback of how trying different runner sizes impacts the performance of their particular engine, and trial and error is not only the proper way to learn but also the proper way to get an actual feel of what's going on with one's particular engine when adjusting a single variable. This is more satisfying and brings results more quickly than understanding but possibly getting lost in the mathematical description of the actual dynamic behaviour, in my opinion and experience. I have read quite a few posts in the archives where some knowledgeable folks seem to drown into interesting and accurate but perhaps excessively theoretical considerations without having actually tried to modify the intake for the sake of testing and comparing their results with the theory.
drnick's S62 runners are "too long" in the same way that S4 runners are "too long" - they were not designed to maximise higher rpm cylinder-filling, which is of interest for a minority of people who prefer to drive an engine that is more powerful and more responsive on the throttle at higher rpm than a high production number standard engine designed as a compromise to safely satisfy the masses, i.e. to make sales.
Still, I do not understand the cylinder-filling sequence of the S3/S4 intake which alternates between 4 "short" runners and 4 "long" runners. The flappy introduced on the S4 intake closes at 5000 rpm most likely to limit the Helmholtz effect which will be counterproductive at higher engine speed due to the "too long" runners.
drnick's S62 runners are "too long" in the same way that S4 runners are "too long" - they were not designed to maximise higher rpm cylinder-filling, which is of interest for a minority of people who prefer to drive an engine that is more powerful and more responsive on the throttle at higher rpm than a high production number standard engine designed as a compromise to safely satisfy the masses, i.e. to make sales.
Still, I do not understand the cylinder-filling sequence of the S3/S4 intake which alternates between 4 "short" runners and 4 "long" runners. The flappy introduced on the S4 intake closes at 5000 rpm most likely to limit the Helmholtz effect which will be counterproductive at higher engine speed due to the "too long" runners.
10-25-2018, 11:42 AM
#50
Well, I have reread your post multiple times and sorry but I cannot see any sarcasm at all.
You raise some good basic points but you did not seem to realise that my outlook was already beyond those, though perhaps that's because my first post in this thread was perhaps not worded correctly in the first place. Sorry again.
You raise some good basic points but you did not seem to realise that my outlook was already beyond those, though perhaps that's because my first post in this thread was perhaps not worded correctly in the first place. Sorry again.
10-25-2018, 04:10 PM
#51
Drifting
Thread Starter
Thom, I would say the difference between these runners and stock is like night and day when driving. I did not have access to a lot of different runners - these were it. In fact I did not have much time either and the car sat for 18 months with no intake! I suppose these were a part of my real world test parameters 
Alex Popov did trial a shorter runner on his engine.
Alex Popov did trial a shorter runner on his engine.
11-08-2018, 08:22 PM
#52
Rennlist Member
I would say that the stock S62 runners you are running at the moment are too long for top end power, if this is what you are after.
It's not hard for me to imagine that shorter runners of equal length will give better top end breathing than the bizarre stock intake with its unequal length runners.
The firing order shows that the 4 "short" (or same side) runners (5/4/8/1) are being fed alternatively to the 4 "long" (or opposite side) runners (3/7/2/6).
This means the charge effect is not optimised to work best either at low/mid range (with 8 equal length "long" runners) or at high rpm (with 8 equal length "short" runners), and that's without even mentioning load losses due to bends. If the flappy, when open, is supposed to improve charge effect at low load, it's no going to help at all at upper rpm because the runners remain too long, and probably the reason why it is programmed to close at 5k rpm on a stock engine.
Sorry if this is not the right thread to discuss it, but what do experienced 928ers think about it?
It's not hard for me to imagine that shorter runners of equal length will give better top end breathing than the bizarre stock intake with its unequal length runners.
The firing order shows that the 4 "short" (or same side) runners (5/4/8/1) are being fed alternatively to the 4 "long" (or opposite side) runners (3/7/2/6).
This means the charge effect is not optimised to work best either at low/mid range (with 8 equal length "long" runners) or at high rpm (with 8 equal length "short" runners), and that's without even mentioning load losses due to bends. If the flappy, when open, is supposed to improve charge effect at low load, it's no going to help at all at upper rpm because the runners remain too long, and probably the reason why it is programmed to close at 5k rpm on a stock engine.
Sorry if this is not the right thread to discuss it, but what do experienced 928ers think about it?
I designed the ITB system that Nick is using.
My 5.4ltr 12.5:1 GTS engine makes 435rwhp at 7000rpm and 500Nm at the wheels at 5200rpm using European Shell V-Power 100RON and the map is frankly **** - I think there is more on the table.
Also, even though I have much lighter JE Pistons in there and 2R rods, I am not sure I would want to spin the stock GTS crank much higher than 7000rpm.
We tried shorter trumpets, we also played with their length - the engine felt worse than a US 1978 Auto with blocked cats and fouled plugs.
All along, simple software told us that the S62 runner length is nigh on optimum, especially considering ITB diameter and injector placement. However, we thought we were smarter than some very smart guys and we got punished - 3hrs of wasted dyno time, countless runs and the car was nearly torched as I just hated the way it performed.
Another UK car had the same ITB set-up fitted and it was mapped by Wayne Schofield of Chipwizzards fame - if anyone knows how to map a car in the World, Wayne is probably one of them. Stock GTS engine, GT cams and 928 Intl headers into and X and then 2.25" dual exhaust - made 390-odd rwhp on a real dyno. The powerband went North as well as peak torque...
11-09-2018, 05:27 AM
#53
Well, that's good feedback.
The point I would mostly like to make about runner length though is that it should not impact peak numbers by itself, all other thing being equal (particularly cam profile and cam timing), but rather how the engine accelerates through the rev range. From what I have read on here and in the WSM, the Helmholtz effect as varied through the flappy's hysteresis control affects the shape of the curves but peak torque remains the same figure whether the flappy is open or closed.
(By the way, when the WSM shows that peak torque rpm varies by a whopping ~1000 rpm with the flappy open/closed while peak hp rpm remains the same tells just much how remarkably restrictive up top the stock intake can be).
The interesting power figures you mention are I think mostly due to engine compression, cam profile and timing, exhaust flow, peak runner flow, though not runner length which is the dimension on which the Helmholtz effect will have a varying impact.
It is a little annoying to read that you think your maps are **** even though you reached some pretty decent numbers on your special GTS engine, as it does not tell if any differential approach and testing has been done by varying cam profiles, cam timing and ignition timing to find the sweet spot for the S62 ITBs to shine through. If you put hours of testing by adjusting such variables until reaching the numbers you mention please stress this otherwise I would tend to think you have reached some kind of lucky result without being actually sure how you actually got there. I'm not saying that gives any less credit to the results reached by the ITBs over the standard intake but it becomes a bit difficult to say for sure they are of the optimum length on any of the engines they have been tested so far, again all other things being equal.
At this point my feeling, my two pence worth obviously, is that the much better than stock dyno results you got on several engines with the S62 ITBs is mostly due to their most likely superior (static) flow capacity over the standard runners, which flow only about 245 cfm as stated on the 928M website. I believe you could gain more engine "top end liveliness", i.e. reducing the time needed for the engine to accelerate between peak torque rpm and peak power rpm, with trying shorter runners. This involves though that your ignition map is already right on the money otherwise you may not be able to reach conclusive results by varying your ignition profile in a differential way that makes any scientific sense.
The point I would mostly like to make about runner length though is that it should not impact peak numbers by itself, all other thing being equal (particularly cam profile and cam timing), but rather how the engine accelerates through the rev range. From what I have read on here and in the WSM, the Helmholtz effect as varied through the flappy's hysteresis control affects the shape of the curves but peak torque remains the same figure whether the flappy is open or closed.
(By the way, when the WSM shows that peak torque rpm varies by a whopping ~1000 rpm with the flappy open/closed while peak hp rpm remains the same tells just much how remarkably restrictive up top the stock intake can be).
The interesting power figures you mention are I think mostly due to engine compression, cam profile and timing, exhaust flow, peak runner flow, though not runner length which is the dimension on which the Helmholtz effect will have a varying impact.
It is a little annoying to read that you think your maps are **** even though you reached some pretty decent numbers on your special GTS engine, as it does not tell if any differential approach and testing has been done by varying cam profiles, cam timing and ignition timing to find the sweet spot for the S62 ITBs to shine through. If you put hours of testing by adjusting such variables until reaching the numbers you mention please stress this otherwise I would tend to think you have reached some kind of lucky result without being actually sure how you actually got there. I'm not saying that gives any less credit to the results reached by the ITBs over the standard intake but it becomes a bit difficult to say for sure they are of the optimum length on any of the engines they have been tested so far, again all other things being equal.
At this point my feeling, my two pence worth obviously, is that the much better than stock dyno results you got on several engines with the S62 ITBs is mostly due to their most likely superior (static) flow capacity over the standard runners, which flow only about 245 cfm as stated on the 928M website. I believe you could gain more engine "top end liveliness", i.e. reducing the time needed for the engine to accelerate between peak torque rpm and peak power rpm, with trying shorter runners. This involves though that your ignition map is already right on the money otherwise you may not be able to reach conclusive results by varying your ignition profile in a differential way that makes any scientific sense.
Last edited by Thom; 11-09-2018 at 05:49 AM.
11-09-2018, 10:45 AM
#54
Developer
Given the engine's displacement, compression ratio, cam profile, intended usage of the vehicle, etc, specifically, what should the runner length, slope, and inside diameter be?
Did you want a peaky power band, or a broader power band that is smoother over the range? And what is the power range you want? In some cases when I design an intake manifold I start with the FDR and the gearing and bring that info forward to tell me where I will want my peak power to come in at. In other cases, like a street manifold, its much simpler to simply want a broad and smooth power band in the primary range of the motor. Tweek it a little for the driver's preference, and you're good.
11-09-2018, 11:37 AM
#55
Rainman
Rennlist Member
Rennlist Member
My 5.4ltr 12.5:1 GTS engine makes 435rwhp at 7000rpm and 500Nm at the wheels at 5200rpm using European Shell V-Power 100RON and the map is frankly **** - I think there is more on the table.
Also, even though I have much lighter JE Pistons in there and 2R rods, I am not sure I would want to spin the stock GTS crank much higher than 7000rpm.
Also, even though I have much lighter JE Pistons in there and 2R rods, I am not sure I would want to spin the stock GTS crank much higher than 7000rpm.
that's a TON of power from only 5.4L...very nice !
do you happen to know roughly the length of those BMW runners that are being used?
11-09-2018, 05:08 PM
#56
Drifting
Another UK car had the same ITB set-up fitted and it was mapped by Wayne Schofield of Chipwizzards fame - if anyone knows how to map a car in the World, Wayne is probably one of them. Stock GTS engine, GT cams and 928 Intl headers into and X and then 2.25" dual exhaust - made 390-odd rwhp on a real dyno. The powerband went North as well as peak torque...
Okay, well, it has ITB's - as stated in the first sentence...
Therefore, for a stock-ish engine, one can see that an intake replacement can be worth 60 rwhp, a very nice gain!
But, it certainly doesn't come cheap with all the required hardware, fabrication, and tune.
11-09-2018, 05:57 PM
#57
Pro
I had to reread this several times to understand what you said. I saw 'stock GTS engine', GT cams, etc. with a tune making 390 rwhp and was incredulous - how can that be? That combo would typically make approx 330 rwhp.
Okay, well, it has ITB's - as stated in the first sentence...
Therefore, for a stock-ish engine, one can see that an intake replacement can be worth 60 rwhp, a very nice gain!
But, it certainly doesn't come cheap with all the required hardware, fabrication, and tune.
Okay, well, it has ITB's - as stated in the first sentence...
Therefore, for a stock-ish engine, one can see that an intake replacement can be worth 60 rwhp, a very nice gain!
But, it certainly doesn't come cheap with all the required hardware, fabrication, and tune.
11-09-2018, 06:11 PM
#58
Rainman
Rennlist Member
Rennlist Member
perhaps minor but "every bit counts"...the 928 with those long hoses running from the air filter up to the radiator will have some pressure drop especially at high airflow demand (WOT/higher RPM).
say 14.5 psi is ambient, by the end of those hoses, through the filter and down into the valley you might be getting 14? at the throttle plate.
curious to know if anybody has measured that.
say 14.5 psi is ambient, by the end of those hoses, through the filter and down into the valley you might be getting 14? at the throttle plate.
curious to know if anybody has measured that.
Last edited by V2Rocket; 11-09-2018 at 06:55 PM.
11-10-2018, 04:38 AM
#59
Pro
perhaps minor but "every bit counts"...the 928 with those long hoses running from the air filter up to the radiator will have some pressure drop especially at high airflow demand (WOT/higher RPM).
say 14.5 psi is ambient, by the end of those hoses, through the filter and down into the valley you might be getting 14? at the throttle plate.
curious to know if anybody has measured that.
say 14.5 psi is ambient, by the end of those hoses, through the filter and down into the valley you might be getting 14? at the throttle plate.
curious to know if anybody has measured that.