For the past couple of years I have been running the same boost gauge (autometer) and its been pretty close to the MAP sensor reading in the datalogs. I have been using the DIY 4Bar kit with the motorola sensor. A couple months ago I changed my set up to a larger turbo, topmount, backdoor intercooler and I also re did my vacuum lines with the push-lock air fittings and tubing. I headed back to the dyno to retune and started boosting off the wastegate spring. As we made a pull I watched the boost gauge and it was reading 7-8psi all the way to redline but the datalog shows it was boosting ~11.5psi. We did a couple more pulls and it was the same thing. I decided to stop tuning until I could figure out why it was so off. I figured it was my DIY MAP sensor so I ordered a new Omni 4Bar even though my volt meter said the DIY Map was good. I installed the Omni sensor and did a couple pulls on the street and datalog them. Well, it still shows ~11.5 psi!!!! Could my boost gauge have gone bad just all of a sudden? Would having some vacuum leak in the new lines cause this? I want to make sure the S300 is reading the correct boost I am running. I dont want to have to buy another boost gauge and find out that is not the problem either.

 

2 different maps and 11.5psi

1 boost guage 7-8


i would trust the map/datalog

 

double check your vacuum lines, there may be a pinch somewhere if both MAPs are reading consistently.

 

Thats my thought too but I didnt touch the boost gauge or its vacuum line. The gauge still sits at zero when off and reads vacuum fine. I'll make sure there are no kinks in it then.

 

does vac on the guage read the same as map?

 

What boost should you be at? You said your running of just the wastegate, so whats the wastegate pressure suposed to be?

 

wastegate has an 8psi spring. Vacuum on gauge and map are about 2 in/hg off. It made 374hp on the 11.5psi that it shows it is boosting. The turbo is an SC61 and before it was a 60trim which made 360ish on 10psi. That makes me think that it is actually boosting the 11.5psi but since it is a bigger turbo it may be making that power at 8psi.

 

My GReddy Boost Gauge reads a good bit higher than my AEM 3.5Bar Map, there was a thread about this a few months back and several people came forward and said their gauge reads higher than their Logs.

 

My gauge reads lower. I guess I'd feel better tuning off the sensor reading than the gauge. I am going to turn up the boost to 15psi on the datalog and see what the gauge reads. If its still really off I am just going to take it out.

 

maybe u don't have the correct voltages in your software. So it's interperating the amount of pressure with a false voltage.

Example:

On a 0v-5v scale

Sensor1. Has a 0-10 sweep

Sensor2. Has a 0-20 sweep

At 2.5 volts:

Sensor1 would read 5
Sensor2 would read 10

make sence?

make sure that the sensor is setup properly in the software

 

i never trust those cheap mechanical boost gauges. I'd just go by the datalogs. Or is there a boost sensor on the dyno? I would expect that to be pretty accurate.

 

I only use boost gauges to give me an idea of boost pressure. If your car can nail a solid 15psi for instance, why would if matter its off? Its not only VERY unsafe to keep your eyes glued to the gauge to prevent a spike, but you likely won't catch it in time. Your car's ems should have the boost cut set & working anyways.

BTW the best way to test different sensors w/o an SSI-4 is to check the output with the key on & engine off. If your electronic sensors read differently, your EMS scaled them wrong (or they're broke). If the gauge is dead-on, then the MFG sold you a very innacurate gauge that was only calibrated for "0psi".


If you guys want very accurate gauges, get the gel-filled gauges from mcmaster.com that only have ~1% variance in the middle 70% sweep and under 1.5% for the edges of reading. They won't look as great, but they will be FAR more accurate. Again, there's little reason to have one if your MAP works fine and boost cut is set.

 

try moving the boost guage with a short tube, inside the engine bay and see if it matches vac.

 

All cars will do this. It is just simply the difference between Absolute and Relative pressure. Just tune off the map sensor.

 

I'm going to side with running925 and say your EMS settings are wrong, and you are in fact still only boosting around 8 psi. You may have the absolute/atmospheric settings wrong, or the voltages as has been suggested. I know the OEM Honda sensor tops out around 11.5 psi, so if your settings are there, then that's obviously where the problem lies.

 

The settings in hondata s300 are correct. I selected the hondata/omni 4bar sensor. The settings match those that came with the new sensor so I know that is not the problem. I will take your advice and just tune off the sensor. Anyone need a 4bar sensor?

 

^ how much do ya want for it