fabrication question

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ProPower engines
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Re: fabrication question

Post by ProPower engines » Tue Mar 13, 2018 1:46 am

Belgian1979 wrote:
Sat Mar 10, 2018 2:11 pm
I need to construct an air bypass line for intake runners. I would like to be able to restrict the airflow if needed. What would be the best way to tackle this ?
PS : I don't have a mill nor a lathe.
Is the purpose of this to adjust or control the air for idle speed better??
There are several air idle control set up's that can be add'ed to control the extra air needed for smooth running if you are currently a bit rich on fuel mixture.
Real Race Cars Don't Have Doors

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Re: fabrication question

Post by Belgian1979 » Tue Mar 13, 2018 2:11 am

ProPower engines wrote:
Tue Mar 13, 2018 1:46 am
Belgian1979 wrote:
Sat Mar 10, 2018 2:11 pm
I need to construct an air bypass line for intake runners. I would like to be able to restrict the airflow if needed. What would be the best way to tackle this ?
PS : I don't have a mill nor a lathe.
Is the purpose of this to adjust or control the air for idle speed better??
There are several air idle control set up's that can be add'ed to control the extra air needed for smooth running if you are currently a bit rich on fuel mixture.
The iac does control air, although the main feed lines (1/2") were only supplying just enough to get a decent idle when cold. But like stated the system as it was (vacuum chamber to which the runner had a connecting hole and which was fed with iac air introduced imbalances which made it run uneven.

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Re: fabrication question

Post by Belgian1979 » Tue Mar 13, 2018 2:13 am

modok wrote:
Mon Mar 12, 2018 11:31 pm
Belgian1979 wrote:
Mon Mar 12, 2018 5:33 am
MadBill wrote:
Sun Mar 11, 2018 9:38 pm
I've synchronized many dozens of IR carb systems and a goodly number of EFI ones and it continues to amaze me how much better they drive (and sound!) when they're synched as perfectly as humanly possible rather than just really close. Among the several devices and listening tubes I've used, the Uni-Syn with various fabbed adapters gets my nod.
One trick that helps with some less well-designed linkages is to sync the throttles first with the idle stops, then use the linkage to just crack them open to verify or tweak the linkage as necessary to ensure synchronization is maintained in the off-idle position.
No matter how good you synchronize them, as soon as the engine warms up the linkage changes a minute amount of length. So what is good in terms of idle rpm when warmed up, is not enough when cold, hence the need for IAC.
So, fix that. It's easy, for me, ok maybe not for you but maybe you could take a picture, we can brainstorm.

And why be so concerned with the idle? I'm more concerned with how it works cruising. You just like to idle?? hmm, I know why.

Emissions testing! right? I used to just adjust everything in the parking lot, then do the test. No more tests here tho.
Cruise is within limits (<5% difference overall in VE, in a lot of places it's around 1%). At idle and transition areas I have up to 20% difference in VE, with the cylinders close to the iac supply running at 15-20% VE difference. The result is uneven running and an engine that tries to hunt.

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Re: fabrication question

Post by modok » Tue Mar 13, 2018 7:54 pm

"Close to IAC?" it will idle better without it. -Independent runners- means they are not connected
I'm not kidding man, try it. Let me know when you figure it out :D
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Re: fabrication question

Post by modok » Tue Mar 13, 2018 8:17 pm

OR......try like this. If this is a four cylinder, 1 and 4 are a pair, and 2,3 are a pair. Three tee fittings. connect one to 1-4, the other to 2,3 then those go to a tee fitting, and to the IAC. It will idle symetrically, but depending on the cam overlap, not necessarily better than not connecting anything.
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Re: fabrication question

Post by Belgian1979 » Sat Mar 17, 2018 5:33 am

modok wrote:
Tue Mar 13, 2018 7:54 pm
"Close to IAC?" it will idle better without it. -Independent runners- means they are not connected
I'm not kidding man, try it. Let me know when you figure it out :D
I understand the concept, but in practice this is difficult. For my fueling calculations at this time I need a map sensor. So this will always create a connection between the runners. The issue with map and itb's is that if you choose a small diameter line and common tube for the map, there will inevitably be an effect caused by intake pulsations. A larger chamber for the map smoothes the pulses that it sees but increases the chances for cross talk. For practical reaons map,IAC and brakes are on the same lines and vacuum chamber

This then brings me to Alpha-N fueling. It is a possibility but the issue here is that pure Alpha-N has not enough resolution at lower rpm ( resolution in the sense of airflow vs TP). On higher rpm it's the other way around, map almost doesn't change whereas airflow does. I've tried both methods but none did work well. I settled on ITB load which uses a mix of MAP and TP where at low rpm more map is used to calculate fuel and at high rpm more TP. This requires me to run a map sensor and associated connecting line/chamber/reservoir.
Bear in mind that this engine stays around 8-10% of TP at cruise. So most of the running is in the 1-10%. When accelerating you move well above 15%.

A MAF would have been a good solution and would have let me do away with the map connections, but the problem is that around 15% the airflow fluctuates wildly in the maf making it's signal unusable for fueling. There could be several reasons for this, but so far I've not found the root cause here. Looks like the ITB-effect is to blame.

Doing away with IAC would require me to set the TP at idle high so that it keeps running above 600 rpm (short of using my right foot) when cold which will create a high idle once warm. The cause here lies in the linkage, which expands when warming up and pulls open the throttles. The additional problem you run into is that once the cars sits for an extended time when hot, the linkage tends to heat up further creating an even higher idle. Originally this created a 'hot' idle of 1500+ rpm. A possible solution could be the throttle stop mentioned above. So far I've had no luck finding anything suitable as most electric throttle stops are of the non-stepper type.

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Re: fabrication question

Post by joe 90 » Sat Mar 17, 2018 6:01 am

MAP/ TPS selection is done by load, not RPM.


Load is MAP with SD
Load is TPS with alpha N.
Load is mass airflow /RPM (A/N) with MAF
RPM is the other axis.

Low load AND low RPM is TPS
Low load AND high RPM is TPS
High load AND low RPM is MAP
High load AND high RPM is MAP

MAF is best, if you're getting a fluctuating load, you're doing it wrong too.

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Re: fabrication question

Post by digger » Sat Mar 17, 2018 6:52 am

Get a good quality contactless tps and set your loads at 0,1,2,4,8 etc increasing the spacing from there to give good resolution at low throttle and less at high throttle it works perfectly fine.

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Re: fabrication question

Post by MadBill » Sat Mar 17, 2018 9:44 am

Belgian1979 wrote:
Sat Mar 17, 2018 5:33 am
.. For practical reasons map, IAC and brakes are on the same lines and vacuum chamber...
Apart from all the other issues and considerations, this will definitely confound the purity of the signal to the ECU. Flow through the IAC will cause a proportional rise in indicated MAP. Visualize a vacuum gauge connected via a small diameter hose to a steady vacuum source, lets say 30 kPa. Now start drilling holes in the line. Every one raises the gauge reading as the leakage increases. Suppose you drill 5 holes. The gauge MAP reading is now lets say 60 kPa. Finally, start blocking off various holes with you fingers, like playing a flute. The MAP reading now fluctuates erratically between 30 and 60 kPa even though the source signal is unchanged.
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Re: fabrication question

Post by Belgian1979 » Sat Mar 17, 2018 10:57 am

Bill,

Contrary to what you say and what seems logical, the map doesn't fluctuate. In fact is very stable and the same kPa as when I used a single plane manifold with carb.

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Re: fabrication question

Post by mk e » Mon Mar 19, 2018 10:57 am

I think where I'll was heading is that the MAP in any 1 tb MUST be fluctuating but the plenum system damps all that out so you never see it.
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Re: fabrication question

Post by Belgian1979 » Mon Mar 19, 2018 2:45 pm

mk e wrote:
Mon Mar 19, 2018 10:57 am
I think where I'll was heading is that the MAP in any 1 tb MUST be fluctuating but the plenum system damps all that out so you never see it.
I think this is correct, but that's the function of the vacuum chamber : to dampen pulses so the signal is stable enough to be used.

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Re: fabrication question

Post by mk e » Mon Mar 19, 2018 2:58 pm

That's right. I don't think there is anything fundamentally wrong with what you're doing, but most anything can be made better

I think you would have an easier time if you sealed the iac valve line and set the hot, no load idle using the throttle so the plates are open a bit more always.....it will just be less sensitive I think.

Cylinder variation is a bugger, especially if it's not consistent so you can't fix it with trim tables. I don't know enough about the MS cylinder O2 setup....that can't help you?
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Re: fabrication question

Post by Belgian1979 » Mon Mar 19, 2018 3:24 pm

mk e wrote:
Mon Mar 19, 2018 2:58 pm
That's right. I don't think there is anything fundamentally wrong with what you're doing, but most anything can be made better

I think you would have an easier time if you sealed the iac valve line and set the hot, no load idle using the throttle so the plates are open a bit more always.....it will just be less sensitive I think.

Cylinder variation is a bugger, especially if it's not consistent so you can't fix it with trim tables. I don't know enough about the MS cylinder O2 setup....that can't help you?
the problem is that it is inconsistent. And the leanest cyls tend to misfire. It corrects, and then it runs fine for a while and it starts again. So this is something that I need to figure out.

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Re: fabrication question

Post by Kevin Johnson » Mon Mar 19, 2018 6:23 pm

MadBill wrote:
Sat Mar 17, 2018 9:44 am
Belgian1979 wrote:
Sat Mar 17, 2018 5:33 am
.. For practical reasons map, IAC and brakes are on the same lines and vacuum chamber...
Apart from all the other issues and considerations, this will definitely confound the purity of the signal to the ECU. Flow through the IAC will cause a proportional rise in indicated MAP. Visualize a vacuum gauge connected via a small diameter hose to a steady vacuum source, lets say 30 kPa. Now start drilling holes in the line. Every one raises the gauge reading as the leakage increases. Suppose you drill 5 holes. The gauge MAP reading is now lets say 60 kPa. Finally, start blocking off various holes with you fingers, like playing a flute. The MAP reading now fluctuates erratically between 30 and 60 kPa even though the source signal is unchanged.
Reaching back in my memory. Yves, wasn't there an earlier issue with your gas tank acting as a cooling-radiator/heat-sink due to radiant heat from your exhaust heating the returning petrol? I am guessing this will also cyclically heat up your booster and thus would be a reason not to have it included in the system.

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