OK, I'm starting another thread with a different question.

My max boost on my gauge has always been 11-12 psi in primary. My vacuum at idle was typically ~19 inches. I've got a Defi mechanical boost gauge.

I plumed a tap off the boost gauge vacuum line to run to the boost sensor for an AVC-R EBC. I used a 1/8th stainless inch tee to make the tap.

Since doing that my gauge (now again with the stock ECU) reads slightly higher boost and slightly more vacuum. 12-13 psi and 20-22 inches.

Was it installing the tee in the line that caused this to change?
If so, would trying to use a slightly larger diameter tee solve the problem?
I'm not sure exactly what the diameter of the boost gauge line is, what is the UIM nipple size?

 

This makes no sense to me.

A restriction in the line could do 2 things: 1) make the reading more steady, and/or 2) cause a slower response. IMO, there is no way it can change the pressure/vacuum in a relatively steady-state condition. And in non-steady-state, it would lower the values. Adding the volume of the line to the BC would also slow response, if anything. Are you sure something didn't happen to the gauge to change its calibration while you were working on this?

Dave

 

dont tee the boost gauge line..

 

After my recent experience, I'm pretty sure that I'm never sure of anything. However, I only cut the boost line, put in the tee, and hooked up the hose the AVC-R boost sensor. What you say makes perfect sense however.

OK. Any suggestions then on where to grab the boost and vacuum readings? Of all the options I had, that seemed to make the most sense. At least to me.

 

Well I have 'T'd mine into the MAP sensor line after the fuel trap-this way,my sensors get filtered air, all my pressure/vacuum readings will be consistent.This was the way I did it in my turboed RX8 and it worked fine.I am using a Greddy
E01.
If I was using a mechanical boost guage I would hook it to the UIM nipple with arestrictor pill in the line to stabilise the reading.

 

My Defi mechanical boost gauge is hooked up to the UIM nipple. It is that vacuum line that I t'd into for the EBC's boost sensor. I'm going to drive the car again today and see if I can some solid readings from the boost gauge. Hard to find a place to drive where I don't have to keep both eyes on the road under wot.

 

I would suggest having a second person in the car to record a video of the boost gauge and tach, that way you can play it back and have a record of the data.

When I do my 40-70 boost checks, I have my girlfriend record the boost gauge and tach so that I can play it back and keep a record of it.

When you saw the 11-12 psi (your baseline), you had no boost controller connected right? Could it be that the default setting in your EBC is causing the different readings?

 

Interesting thought, but how would that have any effect on the vacuum?

Dave

 

I guess what I meant to say was that the default setting for the EBC is allowing a higher boost.

As for the different vacuum readings, they were from different days. We've had a bit of a temperature fluctuation (high 80s last weekend to mid 60s now) recently, could the changes in ambient temperature be the cause?

 

Good idea on the video. I'll see if my son and I can do that. This morning, I had to drive to Oly and saw 11-13 on primary. My secondary is still not boosting well at all, as it drops to about 7. That is hit or miss, some days it does better on secondary than others.

I don't have my EBC connected yet. I just mounted the solenoid and installed the boost sensor for it. I just got the wiring patch harness in the mail today so the next step is to wire-up the patch harness before I tear apart the plumbing to install the boost controller.

I'll get started on that this afternoon.