fabrication question

General engine tech -- Drag Racing to Circle Track

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Belgian1979
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Re: fabrication question

Post by Belgian1979 » Mon Mar 26, 2018 12:45 pm

ptuomov wrote:
Mon Mar 26, 2018 10:49 am
mk e wrote:
Mon Mar 26, 2018 10:04 am
ptuomov wrote:
Mon Mar 26, 2018 9:41 am
On the idle air controller: That needs to bypass the throttle plate. I don't see how the idle air controller can be productively hooked up into this power vacuum canister. Maybe I've misunderstood the intent.
The hoses connect on the engine side of the TB and the check valve allow follow toward to engine so in theory it can work.

In practice allowing the pcv and iac flow into the chamber will drop the vacuum available to the brakes, but I guess he's already got an electric vacuum pump so that will still work...but separating the systems might eliminate the need for the vacuum pump.
I don't think it's a good control system to feed the idle air from the vacuum canister to the intake port with a control valve in the middle. In fact, that's a terrible control system once you consider the operating modes. How's the control system suppose to predict the drop of the pressure insde the vacuum canister and stabilize idle? I wouldn't do that.

As an atlernative arrangement, allowing the IAC to bleed air into the vacuum canister defeats the whole point of having a vacuum canister. To first order, the IAC is going to attempt to regulate the vacuum canister pressure to some level that runs the idle well, which is likely not the level of vacuum that one wants to power vacuum operated devices. That's in my opinion another ill advised control system.

Instead, I'd just have a single hose inlet from the air box (post filter) to a IAC and then a manifold to distribute the idle air to inlets between each throttle blade and intake valve. I assume each throttle body has some idle adjustability one way or another, and the pressure measurement from the vacuum signal ports can be used to equalize the air flow to each of the cylinders.

Each throttle body is going to need three ports between the throttle blade and intake valve. First, the signal vacuum. Second, the power vacuum. Third, idle controller bleed. Need is a strong word, of course. I don't think one "needs" a controlled idle, one could just tune the idle with the screws like in the old times. One could also just use a pump for power vacuum. But I'm sure you're getting my point.
You might have missed some info, but you're not to blame as it's spread over several threads;
Previous setup :
airboxes =>IAC valve=>vacuum Chamber.
PCV +brakes (with one way valve)=>vacuum chamber
MAP and FPR connected to vacuum chamber.
Runners had a hole in them to connect them to the vacuum chamber.

Current setup :
airboxes=>IAC valve=> vacuum reservoir=>one way valve=>runners
pcv+brakes (with one way valve)=>vacuum reservoir=>same one way valves=>runners.
Runners=>map and FPR

The reason why I need the reservoir is I need something to distribute the iac and pcv air evenly.

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Re: fabrication question

Post by Belgian1979 » Mon Mar 26, 2018 12:50 pm

mk e wrote:
Sun Mar 25, 2018 5:37 pm
Progress.

I remember reading somewhere MS lets you sample MAP based on crank angle...can you do that?

If so you could just connect the MAP to a single cylinder and set the angle for the strongest signal at or near idle. That is basically how I pull the individual cylinder data from the output on my multMAP, I read in 30 degree windows. You'd only be getting a signal from 1 cylinder but pulling it when the crank is around 90 degrees down intake should double or triple the vacuum reading you see. Maybe worth a quick try when you get it back together, if it doesn't improve things you can always go with your improved plenum.

There is some downside to only reading 1 cylinder....you add a bit more lag to the signal and it may not be representative if the TBs are way out of sync., but if it helps you can switch to a multiMAP type setup to solve all that if its a problem.
Yes, but it seems that sampling results vary. Didn't try it yet.

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Re: fabrication question

Post by mk e » Mon Mar 26, 2018 1:34 pm

Belgian1979 wrote:
Mon Mar 26, 2018 12:50 pm

Yes, but it seems that sampling results vary. Didn't try it yet.
Might be worth a try. Just 1 cylinder connect directly to 1 MAP and sampled once per cycle. Then play with the sampling angle to get the the best sidnal, but it should be at about 90 degree down the intake, about because the size and length of the hose you use will cause lag.
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ptuomov
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Re: fabrication question

Post by ptuomov » Mon Mar 26, 2018 1:35 pm

Belgian1979 wrote:
Mon Mar 26, 2018 12:45 pm
You might have missed some info, but you're not to blame as it's spread over several threads;
Previous setup :
airboxes =>IAC valve=>vacuum Chamber.
PCV +brakes (with one way valve)=>vacuum chamber
MAP and FPR connected to vacuum chamber.
Runners had a hole in them to connect them to the vacuum chamber.

Current setup :
airboxes=>IAC valve=> vacuum reservoir=>one way valve=>runners
pcv+brakes (with one way valve)=>vacuum reservoir=>same one way valves=>runners.
Runners=>map and FPR

The reason why I need the reservoir is I need something to distribute the iac and pcv air evenly.
Sorry to step in late in the conversation.

I agree that it's an improvement to split the signal vacuum from idle circuit and power vacuum. I think you can further improve the setup by having a separate power vacuum reservoir and idle circuit.

In my opinion, you'll get a better control system by minimizing the volume between the intake port and the IAC valve. Less lag and easier overall control. I'd just use a spider or a tiny log manifold to distribute from one to eight there. If it idles well regardless of the IAC position, this is a less of a concern, IAC will just be adjusting to low-frequency variation in environmental conditions.

Also, the power vacuum reservoir should be a dead end with nothing feeding air into it. If you don't have a lot of vacuum operated accessories, just power brakes, then the reservoir can be small. In my car, everything seems to run on vacuum, including headlights and cruise control, so I've got a big merged bubble cell vacuum reservoir. If you just run a brake booster, I'm not sure you need a much of a reservoir.

Why do you have a PCV valve instead of just breathing the crankcase into the air box?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: fabrication question

Post by Newold1 » Mon Mar 26, 2018 1:42 pm

If it were me I would just by an inexpensive ($125) OEM electric vacuum pump and run the power brake system vacuum off of that. If you just use your multiport intake port vacuum to operate your single MAP (average vacuum from all ports run thru your plenum canister and then run separate lines to your IAC PWM controlled from the ECM .

Then the Map signals are separated from the IAC (less fluctuations in MAP vacuum signal when IAC opens and closes)and your MAP readings should be smoother and the separate vacuum source from the brake booster will also not throw vacuum change (pulling vacuum)pulses directly into the map as the booster opens and closes on brake pedal application. I think some of the ideas here are getting more complex and complicated than they need to be.

As one of my mechanical engineering professors once imprinted on me "Never design or build anything more complicated than it needs to be to work! I live by this when designing and building things and it has always served me well! :wink:

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Re: fabrication question

Post by Belgian1979 » Mon Mar 26, 2018 2:48 pm

For clarity : I already use a vacuum pump for the brakes (and other accessoires such as headlights etc), along with their own vacuum reservoir and one way valve connecting it to the engine. I don't want to use only the pump as it makes a lot of noise (hella pump) and since the cars entire vacuum system tends to loose vacuum. The system has worked so far even though I only have about 9-10" of vacuum at idle. Only with prolonged braking at idle the pump needs to kick in.

My original plan was to connect the map to the moroso can as i think it will need some volume to dampen the pulsing in the runners. The modified the fuel rail is something I'm going to try to see how it does in terms of pulsations and it is the only way I can use one way valves in the lines from the runners to the moroso can. I cannot use the one way valve in anything where the map is connected to.

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Re: fabrication question

Post by ptuomov » Mon Mar 26, 2018 4:35 pm

Belgian1979 wrote:
Mon Mar 26, 2018 2:48 pm
For clarity : I already use a vacuum pump for the brakes (and other accessoires such as headlights etc), along with their own vacuum reservoir and one way valve connecting it to the engine. I don't want to use only the pump as it makes a lot of noise (hella pump) and since the cars entire vacuum system tends to loose vacuum. The system has worked so far even though I only have about 9-10" of vacuum at idle. Only with prolonged braking at idle the pump needs to kick in.
If you have a vacuum reservoir and a pump, you'll just need a little extra, right? If there's not a lot of flow, I think (but do not know) that you could just connect one intake port to that vacuum reservoir with a check valve. As long as there's little to no flow, there's no need to connect all eight cylinder to the system. Brake booster is a very good application for intake port vacuum, as usually the brake assist is only needed when the throttle is closed and rpm reasonably high. At high rpm and throttle closed, the intake port is going to be under a fair amount of vacuum.

If one were emulating 1980's German engineering department, there are of course a number of ways to complicate the system. For example, one could add a venturi jet pump to the brake booster circuit. That would now have more flow, but also higher vacuum. The added flow would make it necessary to connect all eight cylinders to the system, so now you have an extra spider on top of the engine!

There's a similar tradeoff between complexity and functionality in the crankcase breather. You could just connect a hose without any valves from a well-baffled location to the air box. Or, with much greater complexity, pull crankcase gasses thru a restrictor orifice (or PCV valve) into all eight intake ports and then have a second, bi-directional line from the crankcase to the air-box. The more complex system sets up more continuous air flow thru the crankcase, so that's what the factory engineers prefer to do.
Belgian1979 wrote:
Mon Mar 26, 2018 2:48 pm
My original plan was to connect the map to the moroso can as i think it will need some volume to dampen the pulsing in the runners. The modified the fuel rail is something I'm going to try to see how it does in terms of pulsations and it is the only way I can use one way valves in the lines from the runners to the moroso can. I cannot use the one way valve in anything where the map is connected to.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: fabrication question

Post by Belgian1979 » Thu Apr 12, 2018 1:41 pm

I was able to start up the engine the first time and warm it up completely after redoing the intake. Had some issues to iron out as it wouldn't run properly the first time.

Anyway, vacuum is increased from ca. 68-69 kPa to around 60-62 kPa so quite an improvement. Throttle (no driving) seems crispier and engine seems more responsive overal with the induction working better. However that's only the impression.

Still need to iron out several smaller issues though. I experience the problem that one pair of TB's seems to want to go to a higher airflow than the other pair of TB's on the same bank no matter if I closed the throttle it seems to want to rebalance itself at the higher flow. I then just set the lower flowing pair to the same number by opening and setting the TB's on the opposite bank to the same airflow. Works for now, but AFR's are still uneven. The issue here is that in a pair the throttle blades are on the same axle so they cannot individually be adjusted by turning the blades.

What I think happens is that they steal air through the vacuum reservoir. I still haven't received my one way valves so cross flow is bound to happen via the reservoir. And it's a big flow apparently, to the tune of 15-18% in some cyls (especially 3-5 and 7)

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