Tuning for more displacement

[DanGTP]

On my '97 I don't see anywhere to adjust the engine displacement. What do I need to do in order to compensate for a .020" bore on my GTP?

[gtp_cc]

I would think you would just have to add some fuel. The larger bore will let more air in so you will need more fuel. That is how i see it.

[DanGTP]

I've done the fueling, and the car is running fine, I just have an entire column in my spark tables that I can't use because my air mass is maxing out around .80 g/cyl. The far right column of .92 is no longer being hit.

I can post up my most recent tune and scan if anyone is interested in looking it over and seeing if there is something I'm doing wrong.

[Perforator]

Airmass is calculated from airflow and rpm so I don't think displacement would help. Why don't you post the bin and scan up so we an see.

[DanGTP]

Here is the current tune and the most recent scan I took.

The car is a '97 GTP with 9.5:1 diamond pistons, 4" semi-FWI, N* TB, XP cam, ported blower ported LIM, ported heads, 3.4 pulley, P-Log w/ 3" DP.

[Perforator]

You never went over 62% throttle. You're not going to hit the last column unless you hit the throttle. I think you have a problem with your 02 sensor to, it's not switching enough, it seems high.

[Perforator]

Here is your 02



Here's mine from a recent scan



See how your median is much higher.

[DanGTP]

The o2 is a new Denso unit I picked up about a month and a half ago. I just did a short scan on my way home from work. Here it is.

Edit: Take a look at my o2 levels under WOT. I've added fuel a few times and it hasn't seemed to bring the numbers up a whole lot. Also, sometimes I scan the car, the fuel trims will be extremely close to zero, then other times they'll be like they are in this scan - off quite a bit.

Edit2: What would cause my Airmass to plateau? It jumps to .77 as soon as I go WOT, but barely increases after that.

[Perforator]

Your 02's seemed to be switching better in that scan. I think you have a problem with the MAP sensor. It never reads over 160kpa WOT. Have you checked the hoses that go from the MAP sensor to the manifold and boost bypass valve for cracks or leaks.

[DanGTP]

8.5 psi is about what I should be running. I only have a 3.4" blower pulley with an XP cam. I can't go too high on the boost due to the 9.5:1 compression I'm running.

I went ahead and checked the lines. They're in good shape. I replaced all my vac lines when I finished rebuilding the engine in March.

[DanGTP]

I figured it out!!!

The upper portion of my MAF table was still somewhat based off of my old tune, when I had a stock TB. So, everything before PE was dialed in, but since I didn't start with a stock N* table or carry the changes out to the end, it was calculating WOT airflow off my old stock TB values. I've fixed the MAF table, and now the g/cyl values read out properly and the .90 column is being hit again.

[Perforator]

You should get a wideband.

[DanGTP]

I've got a loaner available to me as soon as my roommate gets a new sensor...
But, yes, after I get a new set of injectors, a WB will be my next investment.

[awillis98]

Widebands are a must. there are worth everypennie. buy your own because once you start tunning with a WB you won't want to leave have without it.

I've have mine as a stock o2 sensor replacement for almost 2 years now with no issues.(PLX)

[DanGTP]

The PLX is what I'm planning on buying. I just have to get enough injector for my car first. If I go anything over 75% throttle and 5000 RPM, I'm looking at 100+% IDC!!!