DB2-R81

Can anyone provide me with an approximate value for vacuum, (MAP sensor reading) I should be looking for on a stock B16 at idle?

I am attempting to get started tuning my engine with a S300 and I seem to be into the 7-8th column on the stock base map and I have a hunch my manifold vacuum reading is way low at idle.

0mtber

iTrader: (2)

Around 21 inches of vacuum at sea level is normal.
Do you have a wideband installed on the vehicle? What air fuel ratios are you seeing at an idle ?

DB2-R81

Thanks for the reply and numbers,
Yes, WB O2: PLX M500
Idle air fuel ratio: 10:1 - 11:1

I have attached a couple of short data logs and a P61 stock base map calibration.

My B17 is close to stock only applicable changes:
ITR cams
Skunk2 cam gears
ITR intake manifold
Spoon 4-2-1 header
S2000 TB
42 psi FP

0mtber

iTrader: (2)

Remove some fuel from your idle to see if the motor starts pulling more vacuum.

zman

11:1 AFR at idle!!!!

Thats way too rich dude.

My b16 with the stock cams pulls like 22-24 inches of vacuum at idle, with the stage2 cams I was using it was pulling like 18 inches of vaccun at idle.

I usually tune the idle for like 14.5-15:1 AFR and will usually be in the 2-4 columns.

DB2-R81

Hello zman,

Rich...., now tell me some thing I didn’t know!

I would think on a stock base map from Hondata would not be pushing so much fuel?
I would think a stock base map idle settings would be close to correct for a stock engine?

Now is the map to rich to begin with? Do I have a vacuum leak?

I thought fuel enrichment was mainly based on vacuum and that is why I began by questioning my vacuum readings?

Hello mtber,

Thanks for the response, I will try pulling some fuel and let you know what happens.

Tomdata

make sure you have the proper map sensor selected. If you have the wrong map sensor selected you will appear to have the wrong vacuum readings.

zman

I've never really found any software to have basemaps that startup and run every car perfectly, this is why tuning is so important. You have different cams, intake manifold, throttle body and header, so what makes you think a stock b17 basemap even should run your car perfectly? Your engine is no longer stock.
If you had a vacuum leak the AFR's would lean out some, due to the extra air being added via the vacuum leak.

DB2-R81

Looking at my data logs my MAP readings remain constant at -4.3 psi while idling. Does this indicate a problem with my MAP sensor? I am not receiving any codes. Is there a test procedure to check the viability of a MAP sensor or just remove and replace? No the TPS wires are not reversed.

zman

where does the MAP sensor get its vacuum from? the throttle body?
is it mounted on the top of the throttle body?
or does it have a vacuum line going to it from a vacuum source somewhere?

i've seen in the past where nipples on the throttle body weren't producing any or very little vacuum and had this same issue. I thought my MAP sensor wiring was all ****y b/c I wired up a motorolla 2.5bar MAP on this one car and it was getting very very little vacuum readings. Changed the vacuum source to a nipple on the intake manifold and problem solved.

DB2-R81

Thanks once again for the reply, it is a S2000 TB and the MAP sensor is mounted directly on the TB.

I extended the wiring many moons ago and the engine ran fine with the stock ECU before the S300 replaced it. I also checked the connections from MAP sensor connector to ECU and they are good.

I have an older firewall mounted MAP sensor hanging around and I am going to dig it out, attach it to the manifold and see what range of readings I can record.

b20beast83

I am at about 19 inhg

is this okay guys?

drewbie57

It's ok, I guess. Seems like it isn't quite enough vacuum but if you have a list of mods, it may be reasonable.

DB2-R81,
If you can get a voltage measurement from the MAP when the key-in-engine-off as well when the car is idling that may be able to tell you if the MAP sensor is working properly or not.

I doubt a sustained vacuum leak would let your car idle at ~9"Hg vacuum without surging but it would be a good idea to tighten up those bolts on the TB.

BTW, have you tuned your IACV yet? Is the throttle adjusted properly?

b20beast83

Car idles very good i guess.

Stock b16a with type r cams.

Short ram, exhaust

b20beast83

Car idles very good i guess.

Stock b16a with type r cams.

Short ram, exhaust

zman

19 inches is OK, but I get about 22-24 inches with my stock b16 cams, but i've got slightly higher compression that stock (roughly 11.5:1 CR).

DB2-R81

Just wanted to update, I retested all my MAP sensor connections and it turns out I had a short in one of my MAP sensor wires. I am now seeing correct vacuum readings out of my MAP sensor and the engine runs much cleaner.

With the minimal bit of idle tuning I tried yesterday after correcting my MAP sensor problems, I apear to be having some fluctuations in my air fuel ratio at return to idle. I could remove or add fuel to my maps to get the air fuel ratio to 14.2 and allow the engine idle at a constant RPM and the air fuel ratio readings would remain constant. However if I taped the throttle and let the RPMs fall back to idle I would see different air fuel readings than before increasing engine RPM.

Didn’t have enough time to do through testing last night to figure out what the issues are but I will try and post up some data logs latter today.

Wdbjr12345

That is a map sensor issue or a wirin.g issue I had the same problem