Now that my car is running, I want it running 100%. I just bought tunercat and I'm going to make some adjustments to the car this weekend. However, I realize the need for a better bypass valve because number 1, the car surges at light throttle and low rpm, and number 2, that bosch valve they give you is crap. I had the idea of using a mitsubishi blowoff valve from a 1st generation DSM. On a DSM car, they hold 18 psi and 21 psi with some modification. BUT, physics tells me that at the same pressure level my trans am is gobbling a whole lot more air than my little 2.0 eclipse can. Is that 18psi rating still valid? Could I use a dsm blowoff valve on my trans am???

On another note, if anybody knows how to improve cold idle I'm all ears. When cold, the car is choppy and unresponsive. I assume it has to do with my camshaft (227/239 560/577 115lsa). Any advice is appreciated on either topic.

 

If your BPV is working properly (open under vacuum) I don't see how it could contribute to surging. It is probabally what everyone around here calls 'cam surge'. My 218-230-114 does it a bit in 1st creeping down my dirt road ~ stock tune. I guess there are ways to program the surge out by playing with ignition timing under light-throttle-low-rpm conditions.

Also, make sure the BPV is WORKING. I decided to vent mine to the atm and found it was venting NOTHING! The valve was 10 years old......got a used replacement and it works great.

Is that a CM cam? Looks familiar, but on a 115. I'd really be interested in how you car runs with that cam. The 224-236-114/115 (low or high lift) seems to be a favorite.

Maybe look into a used Vortech Mondo?

Take care,

-Scott.

 

The surge is most likely cam surge. You should be able to tune it out.

The bypass shouldn't cause any surging unless it's stuck closed. I believe the BOV rating of 18 psi would still be valid though I wouldn't replace the bypass on a supercharged car with one.

As far as the cold idle, try adding 1 or 2% fuel to the VE table and see if that clears it up.

 

Okay I am looking at tunercat right now. To get the surge out, I am looking at the table called "Main Spark Advance vs. RPM vs. MAP). That is the one correct? To change it, I would highlight the cells from 400-1800 rpm and 25-45 kPa (or wherever my car idles at) and decrement them a couple of degrees? Does that sound about right? Do I need to smooth the transition to the next levels or is that going to be okay?

As for the cold startup, I am looking at the table called "Volumetric Efficiency vs. RPM vs. MAP". I assume that's the right one... I'd then highlight from 400 to maybe 3500 rpm and 25-70 kPa and scale it by 1.02 for a 2% change. Would that be the right way to do it? By the way, the cam makes about 14-15 in Hg at idle. (http://para.noid.org/~lj/PCM%20Tutorial/Units.htm)

As for the cam, I don't have the experience of my car with the 224/236 114 cam to relate to, but I can say that I am more than satisfied with the powerband that this cam has given me. I did in fact get it from CM. I have big plans in the future and I thought that cam would better accomdate them. Keep in mind that right now the car has stock gears and stock heads, which will change soon along with the bottom end, but even so, it pulls hard down low and behaves pretty well driving around, with a good tune, even better. But the best part is the mid-high range. I haven't dynoed the car yet but from the seat of my pants it is going to make some really nice power, which I estimate will peak at around 6300 or so. From 3000-6000 it just screams, you know, when only one tone is coming from the exhaust - the crazy tone I know all of your cars have the crazy tone too. Oh and the cam sounds nice at idle too, and I said before, make pretty good vacuum for a cam its size, which is probably a result of the 115 lsa.

I am pretty sure that the bypass is working because I hear wooshs of air sometimes when i'm driving the car. They are barely audible over the exhaust and valvetrain with those stock valve covers but I hear them. Also if I accelerate in third or fourth and let off the gas without taking the car out of gear there is 0 delay to full vacuum, it's basically instantaneos. I forgot this post was about the bypass

I can't wait to start tuning...

 

Are you scanning it with Datamaster or some other form of reader? That's going to be the easiest way to determine what the car wants to clear up the surge. Just realize that cam, it will probably get a little surge under 1500 no matter what.

You should be able to scale the whole table at once, just make sure the main table doesn't overlap the extended table. I'd bet you're probably idling around 65 kpa or so anyway. Just remember to save your beginning tune so you can easily reload it if you don't like the changes. I usually do a v1, v2, v3, etc... and keep track of what I've done in the notes section of Tunercat so it's easier to remember what was changed between them. It's saved inside the PCM as well.

Oh yeah, you see instant vacuum because the gauge should be reading manifold pressure. The easy way to tell if your valve is working is to start the car, pop the hood, then connect/disconnect the reference hose going to the valve. When it's connected you should feel air coming out of the bypass and no air when it's disconnected. If you have the bypass actually recirculating air to the inlet tube, you will need to uncap it to feel the air moving.

 

Ahh yes I forgot the gauge is tapped into the manifold.

I moved my MAF right next to the throttle body but the vent tube is still connected to the intake. I could remove the pipe if I want. I will check that out too.

I have freescan and datamaster. I think I will use datamaster it seems more useful than freescan but I have really explored all the features. I usually use freescan. In any case, what should I look for to explain the surge?

 

Usually you will see the Sterms bouncing around pretty crazy. Like 120-140 or something like that.

 

If you do need a new bypass, I'm selling an ATI Pro-Flo bypass valve here:

http://web.camaross.com/classifieds/...ct=547&cat=500

 

With a fuel pump going out on me and fouled plugs i was running a 1g DSM BOV and pushed 400rwhp. so yes they work..

 

So why do you have a greddy now?

 

Cause the dsm was not loud enough for me!!

 

haha, it is loud on my dsm! I guess because I'm pushing a lot more boost on the eclipse.

I checked the bypass. It seems to be working fine. With the reference hose connected I got an alternating suck then blow when I covered the outlet of the bypass with my hands. With the reference off, no air was coming out.

I pulled some timing out of the cell 6 region which is where most of the light throttle cruising occurs and it helped a lot. I have a feeling I will never be able to get rid of it fully.

What should I tune to get the part throttle stuff down? I mean I want the car to feel crisp when accelereting from 2500 rpm when I'm not in the powerband of the cam.

Also, in tunercat it seems there are two WOT tables, which are both some function of %change to afr vs. rpm/coolant temp. What units are those, percent? How do you adjust them?

 

My friend just bought a new bypass valve and it did not up his boost anymore, and he couldnt tell any real difference from the one that came with the kit. I think he is maxing his supercharger out because he can only get 9psi max. He is using the vortech ps1 kit or whatever. He is thinking of upgrading the supercharger portion. He also has the cooler kit with his.

 

Vortech bought out Sony?




I don't see how it is possible to "max out" a Vortech at 9 psi. I have an S-Trim and I know they can do a lot more than that Sounds like a pulley swap would fix his problems!