SteveH
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| posted on 20/9/05 at 11:42 PM |
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MAP sensor with TB's?
I know it's here some were, but I can't find it...
I need to know how to "tube-up" throtle bodies to a Map sensor?
Can anybody point me in the correct direction....
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physician
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| posted on 21/9/05 at 01:51 AM |
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someone will back me up, i used on a frien civic with throttle bodies, a canister with the sensor mount on it, and a tube to each throttle body. the
purpose of the can id mainly to give the brake booster a descent vacuum because on a bike they just use a big hose with small tubes feeding into it
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suparuss
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| posted on 21/9/05 at 05:53 AM |
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if it is individual throttle bodiesyou need tubes joining into each of them to even out the signal, if you just link it to one the pressure will
fluctuate like mad.
a canister will help, like phisician said, as a damper for the signal.
russ.
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NS Dev
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| posted on 21/9/05 at 07:35 AM |
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Much "better" idea to not use a map sensor at all unless you are turbocharging/supercharging.
Just use a throttle potentiometer, no need for the map sensor, and no crappy pipes everywhere and more precise to map anyway.
[Edited on 21/9/05 by NS Dev]
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Volvorsport
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| posted on 21/9/05 at 08:32 AM |
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ie - set it up on alpha numeric .
rpm for speed
throttle angle for load
www.dbsmotorsport.co.uk
getting dirty under a bus
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NS Dev
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| posted on 21/9/05 at 09:05 AM |
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that's a quicker way of putting it!
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Volvorsport
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| posted on 21/9/05 at 09:18 AM |
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im a one syllabal wonder
www.dbsmotorsport.co.uk
getting dirty under a bus
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CairB
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| posted on 21/9/05 at 11:42 AM |
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I'm coming to the same conclusion.
I have ITB's and Megasquirt that uses MAP and rpm as the main parameters for determining fuel requirements. It is refered to as the
Speed-Density algorithm which has it's advantages over alpha-n which uses throttle position.
However, I have found that the fuel requirements rise very steeply as the MAP value goes above 90kpa (100kpa approx = atmospheric) which results in a
small change in MAP measurement resulting in a large change in fuel.
I've had a few conversations with other people and I'm coming to the conclusion that this is a physical effect of averaging the pressure
from 4 highly impulsive sources as opposed to case with a common plenum chamber downstream of the throttle.
I have a feeling that most tuners use the throttle pot and rpm as the main fueling parameters.
Meanwhile I'm in the process of flicking over to hybrid alpha-n which combines both throttl position and MAP. The Megasquirt supports several
modes of operation as standard and others with a bit of coding change.
I'd be interested in other peoples views on this subject.
Cheers,
Colin
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Mix
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| posted on 21/9/05 at 11:50 AM |
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The advice I received from Martin Fox, (who supplied my Jenvey bodies and DTA ECU) was to use a throttle pot on a normally aspirated system.
The MAP sensor only really coming into it's own on a turbocharged system.
Mick
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NS Dev
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| posted on 21/9/05 at 01:55 PM |
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I have never seen a map sensor based naturally aspirated system on a competition car, and while I don't build engines for a living, I have seen
a fair few in a few branches of motorsport.
They are almost exclusively tps based.
It was this that initially put me off Megasquirt when I started looking at it around 3 years ago.
Both of my MBE systems are tps and crank speed based.
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MikeRJ
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| posted on 21/9/05 at 05:55 PM |
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MAP gives a far better indication of engine load than a TPS, and also compensates for any wear etc. as the engine ages. You won't find a normal
production road car using Alpha-N (unless in "limp home" ) , even though it would be cheaper to manufacture.
Alpha-N is very usefull when you have long duration/high overlap cams that give low manifold vaccum and large pressure pulses, which is why it's
used almost exclusively on competition cars.
[Edited on 21/9/05 by MikeRJ]
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Volvorsport
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| posted on 21/9/05 at 06:14 PM |
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its easier to set on TPS also , because you can hold the engine at load , and add Boost as a correction factor in MBE cases.
www.dbsmotorsport.co.uk
getting dirty under a bus
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big_wasa
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| posted on 21/9/05 at 10:10 PM |
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Hmm , I was left with this choice for my mega jolt ecu . This was before the new board came out .
I’ve taped in on my manifold where the injectors would sit .I will join all these to a small cylinder which I hope will smooth out the pulse.
An idea I’m going to nick of Paulf is to use a small spent co2 cell , cut the top of and solder on a copper cap .This can also be used as a fuel trap
to stop fuel/air travelling to the map sensor.
Not running yet so not able to comment .But will say that all I have read on the mega ecu range all state that map gives a better indication of load
compared to tps. Unless hardware stops this with high duration cams ect ?
Ps anyone got an empty co2 cartridge I can have as I cant find one....Please...
 
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CairB
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| posted on 21/9/05 at 11:26 PM |
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Just finished a bit of number crunching of datalogs from my setup that may be of interest to those embarking on MAP based control with ITB's.
It seems to confirm my suspicions, and the general comments re performace engines, that individual throttle bodies are probably better on TPS rather
than MAP only, on my engine even with relatively mild cams.
The plots showing the comparison between the 2 methods. If you concentrate on the surfaces of the plots, the significant difference is the way the
with MAP the VE (or effectively fuel pulse width) increases steeply with MAP, ignore the steep sides where it drops to 0, its just where there was no
data. The MAP plot is also missing some high VE points at full map due to resolution of my analysis.
Also this was based on and air fuel ratio of 14.7/1 across the board. When I add the variable AFR to richen the top and weaken the bottom the effect
on the MAP is steeper still.
The RPM scale is identical in both cases.
 
TPS v MAP Fuelling
Hope this is of interest to someone.
Cheers,
[Edited on 21/9/05 by CairB]
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NS Dev
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| posted on 22/9/05 at 07:54 AM |
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That's an interesting comparison.
Going back to what Volvorsport mentioned, and the point that I made.........................go with TPS!
It is much easier to set up, and has much better response at lower loads, as is evident on the graphs above!!!
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SteveH
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| posted on 24/9/05 at 08:45 PM |
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Thanks for all the info.
Now don't throw all your toys out the pram...cuz what I'm doing is sticking TB's on a Ford 8V DOHC....
I was trying to use the slandered EEC IV, this has a MAP sensor. I can tweak the fuelling with higher output injectors & a few known tricks with
the warm-up cycle.
What I've found is some one way air valves with a opening pressure less than 0.5 psi. If I attach these into lines running to bodies 1 & 4,
using the small volume cylinder compensator, I should get a half reasonable MAP reading?
There will be a slow air bleed into this cylinder to normalise pressure for closed throttle bleed. Effectively it becomes a surrogate manifold.
If I enlarge the cylinder & use all the TB's could I use this for the brake servo?
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