SR20DE Block with Neo VVL head and acceleration issues

[NiCoXis]

I just registered to the forum, and I’d like to start by asking for some help 🙂

I have a Nissan Primera (also known as Infiniti G20). Originally it had a standard SR20DE but I’ve done couple of mods to it, Neo VVL head swap, high performance 4-2-1 extractor, Fujitsubo High flow exhaust and a JWT Pop charger.

Bellow are some pictures of the head swap process, which my mechanic did.

My issue is that acceleration acts weird, specially when cold. Just pushing gently on the gas pedal it starts accelerating and then it decelerates (no matter if I push it further down).

The problem is reduced when the engine gains temperature (harder to notice), and it only seems to disappears when going WOT.

I’ve looked for vacuum issues but found nothing. I’m thinking it may be a problem with my injectors being dirty or not mounted correctly, but that’s just guessing on my part (I’m a car newbie).

Any ideas on what

Topic

[NiCoXis]

Actually the regulator came with a gauge, it’s now at 3 bar / 43 psi and doesn’t seem to go down when I’ve tested.

According to the service manual, these are the stock pressures,

At idle speed:
With vacuum hose connected
Approximately 235 kPa (2.4 kg/cm2, 34 psi)
With vacuum hose disconnected
Approximately 294 kPa (3.0 kg/cm2, 43 psi)

I’d like to see what happens with pressure when my engine stalls but it’s kind of difficult to see under the hood and drive at the same time lol xD maybe tape it somehow…

Another thing, can I discard my MAF sensor failing? I’d think that because it would idle horribly and issues wouldn’t alleviate or disappear when engines gains temperature.. am I right?

On a side note, this is the car hehe 😀

Thanks again guys!

[EricTheCarGuy]

If you’re still having an issue that you really can’t rule things out just yet. The MAF takes a direct measurement of the incoming air to determine how much fuel to add, one thing I sometimes find with these systems is that ANY air leaks in the tube that goes from the MAF sensor to the engine will cause performance problems so be sure there aren’t any leaks or loose connections that could allow air to enter the engine that wasn’t measured by the MAF sensor.

[SmopuiM]

Head over http://www.nissanmexico.org since you speak Spanish.

The forum is managed by some people of the best nissan workshop in mexico, and they usually do full swaps from DE to VE all the time plus they are specialized in all kinds of SR engines., so they may able to help, plus they would love to see your work, since its a great car you have been building.

[EricTheCarGuy]

This is the first time I’ve seen the pics of the car come up, I really like it, I wish we had those in the states.

[NiCoXis]

Quoted From SmopuiM:

Head over http://www.nissanmexico.org since you speak Spanish.

The forum is managed by some people of the best nissan workshop in mexico, and they usually do full swaps from DE to VE all the time plus they are specialized in all kinds of SR engines., so they may able to help, plus they would love to see your work, since its a great car you have been building.

Thanks for your comment! I’ll give it a shot 😀

[NiCoXis]

Quoted From EricTheCarGuy:

This is the first time I’ve seen the pics of the car come up, I really like it, I wish we had those in the states.

Thanks Eric! I really like the US G20 side skirts, I’d love to get my hands on a pair of those as they are quite rare here.

Going back to my issue, I installed an innovate wideband and found out that my problem never goes, it just becomes unnoticeable. Last week I was going on the highway at 120km/hr@3.000rpm and my AFR was constantly going from 14 to 16, almost like a pendulum. This happens even at idle, but at a shorter range (13.9-14.5 for example).

Today I’m supposed to be testing a replacement MAF today to see if that’s my problem.

Thanks for everything!

[NiCoXis]

Any suggestions from anyone??C;(

I still can’t test the MAF but I’m guessing that won’t fix it, I think I may have problems with the electronic injection system, is there any way I could troubleshoot it? maybe my ECU is malfunctioning?

[NiCoXis]

Tested a new MAF yesterday, the problem persists 🙁

[EricTheCarGuy]

If you don’t have codes for the MAF or the computer it’s not likely those are at fault. The AF rations you show are actually normal as they will switch rich lean around 14.7 as you drive. So if you don’t have any codes to go on look to the basics like vacuum leaks or tune up item issues.

[NiCoXis]

Quoted From EricTheCarGuy:

If you don’t have codes for the MAF or the computer it’s not likely those are at fault. The AF rations you show are actually normal as they will switch rich lean around 14.7 as you drive. So if you don’t have any codes to go on look to the basics like vacuum leaks or tune up item issues.

Alright, I’m getting a new reprogrammed ECU with a new base map to accommodate all the mods I’ve done, maybe also an S-AFC II to do some fine tuning.

Thanks!

[NiCoXis]

news, installed the new ECU with updated MAP and tuned with Apexi SAFC2, the car performance went up very nicely and the rev limit is now set at 8200rpm with intake cams activating at 4200 rpm and 4600 for the exhaust, so my powerband is now much better fitted for my current setup! 😀

Sadly, my issues still persist….resignation….

[NiCoXis]

The only change is that the problem now happens with a hot engine as opposed to a cold engine that I described when the issue started, I think my engine is playing a prank on me…

[EricTheCarGuy]

Thanks for the update. You may be dealing with a mechanical issue in the engine I can’t remember if you did a leak down or compression test but if not one might be in order.

[NiCoXis]

Quoted From EricTheCarGuy:

Thanks for the update. You may be dealing with a mechanical issue in the engine I can’t remember if you did a leak down or compression test but if not one might be in order.

Last time we measured compression it was good, approximately 185psi for each. I’ll do it once again to confirm it’s alright.

Oh just remembered that today I found that my exhaust manifold is blowing between it and the engine and also changed my spark plugs with colder ones to avoid detonation (had NGK BKR5E, now BKR7E). Don’t know if that might be related…

I think I might need to do an EFI course haha xD

[NiCoXis]

Update:

The hot engine issue was related to a launch control feature failure that reads from a transmission sensor that needs to be replaced.
Removed it and it now works perfect !! I also fixed the blowing exhaust manifold 😀 running like a charm now.

Thanks guys for your help

One quick question though, I need to change my clutch to something more adequate to the performance the car has now (app 200hp from 140 stock), I was thinking about something like this http://www.ebay.com/itm/6-PUCK-SPRUNG-STAGE-3-CLUTCH-SENTRA-200SX-G20-SR20DE-/380420096260?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AInfiniti%7CModel%3AG20&hash=item5892ce0104&vxp=mtr

But I don’t know much about the topic, I’ve heard 4 vs 6 pucks, sprung vs unsprung, can you guys give some guidance?

[Author]

Replies