Nice writeup and install.
One comment: It is NOT a good idea to tee a vaccuum source into the MAP signal line. I would never recommend nor condone that. It might not cause any problems on the surface but it is best to not take the chance. The plumbing of an additional vacuum "volume" into the line going to the MAP sensor can cause signal oscillations and signal errors in many speed density fuel injection systems. This situation with the MAP signal has been tested and developed (hopefully.....) by the factory that developed the fuel injection systems and is best left alone. One specific area of development that any speed density system goes thru is testing of the fidelity of the MAP signal and hose lengths and hose volumes have a VERY definite effect on it and are frequently "tuned" by the factory for optimum MAP signal fidelity.
If you look at OEM fuel injection systems it would be very very rare to find any accessory or vacuum feed plumbed in parrallel with the MAP signal for just such a reason.
It is a better idea to run a separate vacuum supply system for the cruise using the 4 vacuum taps provided for throttle body sync'ing.
You may never notice a problem in normal riding with the extra vacuum volume in the MAP signal line....but then again....it could cause a lean hole in the fuel injection calibration just at a certain WOT point that will be nasty to find one day.....why take the chance.
And one additional idea: The bead chain connector can also be secured when finished with a drop of RTV that will keep the connector from disconnecting. I found that the bead chain wanted to lie a certain way to make sure that no binding/kinking/snagging occurred when the cruise was NOT being used and the throttle was held at WOT....this condition generates the most chain slack and is often a problem with bead chain routing. After determining the best way for the bead chain to route/hang when slack I laced a very thin bead of RTV down the bead chain and let it set up for 24 hours before moving the chain. The RTV adds just enough resilience to the bead chain to "form" it into the desired routing yet it is flexible enough to not affect the operation of the cc.
Jestal,
Thank you for the input and suggestions. I too, was concerned about the 1 ½” X 6” pipe, and the extra intake volume that would be behind the throttle plate when I was thinking about this particular section of my cruise install. I’m also aware that the standard practice is to use one or two of the service ports for throttle body synchronization to provide the vacuum for the cruise.
As you may know, any extra volume in the intake track of any cylinder would increase total volume by the same amount, this will not change if it was hooked up to one or all four. The factory MAP sensor is attached to all four thru T fittings and hoses to get an average manifold pressure reading……and to have the intake pulses closer for a more smooth and stable voltage output for the control unit to calculate fuel and ignition management. Tapping into the sync port of one cylinder would not change total volume but could disrupt the intake pulses and could translate into an unstable output of the MAP sensor because it would look like a vacuum leak in one of the cylinders during vacuum demand for cruise servo operation. I think if there were any chance of “signal oscillation”, it would be under this arrangement and not when its averaged out by all cylinders.
Additionally, I did a before and after comparison with a vacuum gauge to verify there was no difference at all with/without the entire cruise in the system, including canister, and during canister filling after engine startup……there were no noticeable difference with vacuum and vacuum buildup time either way due to the small additional volume required by canister and servo unit. Also note the placement of the check valve will limit the volume to only the small hose between engine and check valve once the canister pressure is equalized or lower than manifold pressure because the valve will retain usable vacuum until it is needed……and……..the amount of vacuum required during cruise operation in setting and maintaining speed is at a level that will not affect MAP output in my opinion.
Respectfully, I disagree that hooking into the service port of one is a better method. The small amounts of air moved is better shared by all 4 cylinders, not only for a smoother vacuum supply for the cruise unit, but less chance of an erratic MAP signal output.
You wrote “If you look at OEM fuel injection systems it would be very very rare to find any accessory or vacuum feed plumbed in parallel with the MAP signal for just such a reason.”
I don’t know what you mean by this. The MAP sensors are always reading manifold vacuum and just about everything related to vacuum (cruise control, pcv system, fuel evap emission control, interior climate control……the list goes on) is in parallel with this sensor. When there’s a vacuum leak, depending on the size, vacuum will be reduced to everything………including MAP sensor.
You wrote “You may never notice a problem in normal riding with the extra vacuum volume in the MAP signal line....but then again....it could cause a lean hole in the fuel injection calibration just at a certain WOT point that will be nasty to find one day.....why take the chance.”
It is a fact that manifold pressure is at its lowest (vacuum highest) during engine deceleration per any given attitude, any other operating condition will yield higher pressures (vacuum lower). With enough load to the engine, you can get close to atmospheric pressure even at a very low engine speeds (closed to idle speed if you try), it is directly related to load and throttle opening angle. My questions: under what condition will the extra volume cause a “lean hole”? And what certain WOT (wide open throttle) point will it cause a problem? Are there more than one WOT condition? As far as I know, WOT……is WOT. My point is, engine manifold vacuum is easily reduced any time the throttle is opened…..and or with load increase…….and reduction of vacuum will result in less affect on any small opening such as the hose to the cruise canister and the canister itself. This is the exact reason why vacuum leaks will affect engine performance more at idle. There will be little air movement (if any) thru small holes at WOT. This should not affect MAP Signal at all since it is already near atmospheric pressure. I think there is little or no risk of performance issues at wide open throttle.
Ps. I keep close track of my fuel mileage, and thus far it has not changed. I don’t think engine management mapping has been affected by the addition of the CC.
I like your RTV idea on the bead chain, any preventive measures in this sensitive area would be good. Good job!
Gordon
You may disagree....but....take it from someone who has developed a number of speed density fuel injection systems that are out driving around in production vehicles you DO NOT want to tap into the MAP sensor signal line.
I really don't mean to argue but I have personally seen sitations where MAP sensors on production systems were relocated, line length, routing and diameter changed, etc.... during development to simply to affect the tuning of the volume in the actual line leading to the MAP sensor to improve fidelity of the MAP signal under transients and steady state conditions. This involves FAR more than simply looking at the signal with a vacuum gauge....LOL. So, it is really not an opinion of mine but a proven FACT that the volume of the hose leading to the MAP sensor is a critical design element of the system and really should not be modified by tapping into that line.
Trying to determine whether the MAP signal accuracy has changed is impossible with a vacuum gauge or by simply measuring fuel economy. Period. You need hundreds of hours on a dyno and in a vehicle with some relatively sophisticated measurement hardware to determine this. YOU have no idea whether you have affected the fidelity of the MAP signal on your system. The kind of glitch that changing the MAP signal resonance will result is impossible to predict. It could be a rich or lean spike on a transient, a steady state hole in the calibration, etc. Completely unknown and unpredictable. That is the basis for my point. Since each install is going to be a bit different and line lengths, diameter and routing unpredictable YOU do not know what is going to be affected on the NEXT PERSON'S install if they use the MAP signal line as a vacuum source. Your's might not be affected and you may not care but it is inadvisable to recommend a vacuum routing that could lead to an unpredictable response on another system.
All speed density systems use the MAP as a fundamental means of calculating the fueling and spark advance for the system. The actual or raw MAP signal is often fraught with noise, overriding transients and fluctuations, etc so "raw" MAP is rarely used. Instead, sophisticated averaging software routines will "filter" the MAP signal based on development data, the sorts of periodic fluctions in MAP the specific system generates...i.e...number of cylinders, plenum volume, etc... to provde the right sort of MAP signal for the various ECM functions. One of the key factors in this calibration and treatment of the MAP signal is the volume in the hose leading to the MAP sensor. If you change this (by teeing in a large volume) you just threw out all the MAP signal processing development that was done for the system.
Yes, vacuum is low at WOT.....but.....MAP is high at WOT. Therefore the fact that there is zero vacuum has little relevence on the MAP reading at the sensor. BARO - Vacuum = MAP At WOT the MAP reading is basically the BARO ( minus some slight loss thru the air cleaner/induction system) with any inputs from the engine side of the system superimposed on it. MAP at WOT is far more active than at idle or heavily throttled areas.
BTW....MAP readings are WOT are far from steady. Take the snubber out of your "vacuum gauge" and see. Even then you can only see a tiny proportion of the noise. There is a lot of instantaneous noise on the raw MAP signal from pressure surges in the intake volume. This changes constantly with the barometric pressure in the local you are in and the rapidly changing RPM of the engine. Production systems are designed to "tune" this out of the MAP signal system. Just suppose.....you add a volume to the MAP signal line (with a tee'd in hose to the cruise) that suddenly (and inadvertently) adds a signficant tuning volume that will magnify certain frequency signals. You might never see this unless the engine dwells at that specific RPM for a period of time. This could easily drive the system rich or lean. This phenonenon is very prevalent on individual throttled systems like a motorcycle so you are recommending an install that is even more likely to cause a problem than on systems that problems have already been observed in the past!!!
The volume of area inside the throttled side of the system is relatively large. Pulling vacuum off of that general plenum area thru a separate port will have FAR less effect on the vacuum signal to the MAP sensor than putting it in parrallel. The small port at the plenum (the MAP signal ports, for instance) will act to isolate the effect of other ports due to it's being a restriction and resonance point or node for downstream resonances or "tuning" problems with the length of line leading to the MAP sensor.
Let me clearify one thing. I don't propose feeding the cruise off of just one of the service ports. It would be best to use all four of them in the same sort of arrangement the MAP sensor uses. Even better, would be to isolate each of the service ports with a one-way vacuum check valve in each port line and then tee the four isolated sources together as the feed for the cruise. That is the way my CC system is plumbed on my FJR and the way that I would recommend doing it. Plenty of vacuum supply with all four port accessed and each port is isolated by the use of four check valves. In reality, with the large vacuum reservoir and single check valve in the system it is probably fine to use just one service port as the only real disadvantage is a reduce vacuum signal...but with the reservoir in the system the reservoir alone will serve to provide cruise function from that vacuum supply with only slight replenishment.
In summary:
"
As you may know, any extra volume in the intake track of any cylinder would increase total volume by the same amount, this will not change if it was hooked up to one or all four." True, but use all four service ports, not just one. Individual vacuum signals from different ports DO tend to be isolated from the other taps by the orifice effect at the plenum intrance. So...tapping off of the service ports WILL isolate the effect of the cruise from the MAP signal.
"Respectfully, I disagree that hooking into the service port of one is a better method. The small amounts of air moved is better shared by all 4 cylinders, not only for a smoother vacuum supply for the cruise unit, but less chance of an erratic MAP signal output." But, why would you introduce a potential tuning problem in the isolated feed to the MAP sensor when it is PROVEN to cause problems in many other cases. Cases you never even knew about because the manufacturer developed it out before you ever saw it.
"I think there is little or no risk of performance issues at wide open throttle." You think wrong. Due to the engine induced pertubations in the induction system MAP the chances of unintentially inducing an undesireable tuning effect in the MAP signal line is greater at WOT than any other time. Think of it like a helmholz resonator that you may create by teeing in an additional volume into the line. What frequency did you accent or attenuate. Don't know??? Better figure it out before saying nothing is going to happen.
"As far as I know, WOT……is WOT." WOT may be WOT but the signals and pressure pertubations induced into the intake plenum volume change constantly based on RPM of the engine. So...WOT at 3000 is not the same as WOT at 8000 when looking at MAP sensor tuning. Not even close.
"You wrote “If you look at OEM fuel injection systems it would be very very rare to find any accessory or vacuum feed plumbed in parallel with the MAP signal for just such a reason.”
I don’t know what you mean by this. The MAP sensors are always reading manifold vacuum and just about everything related to vacuum (cruise control, pcv system, fuel evap emission control, interior climate control……the list goes on) is in parallel with this sensor. When there’s a vacuum leak, depending on the size, vacuum will be reduced to everything………including MAP sensor."
What I mean is that no OEM will tee into the MAP signal line for accessories for the reasons elaborated upon above. No one does this. MAP signal lines are always discrete...for a reason. Thinking you have figured this all out and rationalizing that it is OK to tee into the MAP signal line is an error. Look at production systems and see for yourself. No one tees into the MAP line. As mentioned above, the discrete MAP signal IS isolated from the other influences by the orifice effect at the plenum entrance. Certainly a vacuum leak or other transient will affect the plenum volume and it will also affect the MAP signal accordingly. This is OK as long as the input affects the engine and the MAP is reacting to that engine change in vacuum. To put some unknown vacuum volume in parallel to the MAP signal line (by teeing into it) would introduce MAP errors via unwanted tuning that the engine would NOT see. BAD.
I really don't mean to belabor this but it is text book wrong to tee into the MAP line whether you believe it or not. If it is not causing you a problem then, fine, have at it. But do NOT recommend it to others and attempt to justify it.
Use the service vacuum ports for cruise control feed, do not tee into the MAP line.
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