MAP at idle

[Harley Pilot]

So with an S&S 475 cam my MAP is reading 40-42 at 1000 rpm, is this normal/ ok

[rigidthumper]

Seems a little hi to me, I expect idle MAP to be in the 30s. I'd contact Dynojet, and ask about a base map that has background settings for your cam.
Which map are you using?

[Jamie Long]

So with an S&S 475 cam my MAP is reading 40-42 at 1000 rpm, is this normal/ ok

Normal; zero issue

[Harley Pilot]

Thanks for the replies. Just making sure everything is copacetic!👍

[Harley Pilot]

Seems a little hi to me, I expect idle MAP to be in the 30s. I'd contact Dynojet, and ask about a base map that has background settings for your cam.
Which map are you using?

I'm running a Fuel Moto supplied map.

[Jamie Long]

There is much more to manifold pressure than idle Kpa. When monitoring MAP you need to take the entire operating range into consideration, not just idle. We aim to get MAP normalized as close to actual at WOT (or you may not run all the way up the timing table) and also ensure that we have proper resolution thru out the rest of the operating range, of course including idle. Ive seen users focus on idle MAP many times rather than looking at the whole picture, too low light load MAP can cause several issues including issues with fuel & timing control, with closed loop operation & decel fuel cut, and other factors, this can go the other way as well if MAP is too high. The most important aspect is to have proper MAP thru the cruise range and tip in (rather than idle) and this can/will change by the camshaft as it directly changes engine vacuum. No blanket statement on the MAP the engine should idle at.

While its apples to oranges in comparison, as a side note on Bosch ME17 ECU equipped engines such as the Indian TS 116 in stock form the idle map is 70KPa (yes seventy) and we don't generally run into issues with resolution

[rbabos]

Wow, 70kpa. I'm on the other side of things with stock cam v rods. Most idle at about 24kpa. The SE cams in the mid to high 30s. It is what it is.
Ron

[Jamie Long]

Wow, 70kpa. I'm on the other side of things with stock cam v rods. Most idle at about 24kpa. The SE cams in the mid to high 30s. It is what it is.
Ron

Also very common to see 60Kpa at idle on a cammed LS engine.

An eye opening test is to set up a vacuum/pressure gauge and monitor it vs the reported MAP from the vehicle bus; change the cam and repeat. Better yet connect a second MAP sensor and input the analog signal into the dyno hardware and overlay it with the vehicle MAP sensor data, a lot of long nights here doing that stuff.

[Harley Pilot]

Wow, 70kpa. I'm on the other side of things with stock cam v rods. Most idle at about 24kpa. The SE cams in the mid to high 30s. It is what it is.
Ron

Also very common to see 60Kpa at idle on a cammed LS engine.

An eye opening test is to set up a vacuum/pressure gauge and monitor it vs the reported MAP from the vehicle bus; change the cam and repeat. Better yet connect a second MAP sensor and input the analog signal into the dyno hardware and overlay it with the vehicle MAP sensor data, a lot of long nights here doing that stuff.

👍

[pauly]

HI Harley Pilot,

Here's a recording from an 07 softail I made - thought it may ease your mind. In between 40.6 & 34.6
TEMP    RPM   TPS   MAP   SPARKF   SPARKR
18   1279   0   40.6   26.5   26.5
22   1206   0   36.2   25.75   25.75
25   1136   0   36.9   24.75   24.75
66   1005   0   36.9   21.25   21.25
68   1018   0   36.5   21.5   21.5
96   1012   0   35.1   21.5   21.5
97   973   0   35.4   21.25   21.25
100   944   0   36.2   21.25   21.25
104   1007   0   36.5   21.5   21.5
105   956   0   38   21.25   21.25

113   965   0   36.2   21.25   21.25     
116   984   0   34.7   21.5   21.5
118   1007   0   34.7   21.5   21.5

120   1000   0   35.4   21.5   21.5

Thansk Pauly

So with an S&S 475 cam my MAP is reading 40-42 at 1000 rpm, is this normal/ ok