New "Bigger" cam wants less fuel at idle?

[edcmat-l1]

Correct me if I am wrong but won't the new cam reach a point maybe higher RPMs where it is more efficient than the previous camshaft and require more fuel?

Yes, that is exactly what will happen.

[Midnite Magic]

Yes, that is exactly what will happen.

Feels good that I am catching on slowly

[IDRIVEAG8GT]

In actually learning quite a bit too that I thought I knew

[LSxpwrdZ]

Not really tuning related but my cam math tells me that your new cam shouldn't have as much top end as the previous cam unless the lobes are just more aggressive... the larger LSA creates an earlier EVO and EVC point which ultimately promote top end power and flattening/broadening of the torque curve. Your intake side is identical if the cam specs are accurate. 115+3 LSA gives you a 112 ICL. 112+0 also gives you a 112 ICL. Without changing the intake event's I don't really see much powerband change occuring...

[IDRIVEAG8GT]

Not really tuning related but my cam math tells me that your new cam shouldn't have as much top end as the previous cam unless the lobes are just more aggressive... the larger LSA creates an earlier EVO and EVC point which ultimately promote top end power and flattening/broadening of the torque curve. Your intake side is identical if the cam specs are accurate. 115+3 LSA gives you a 112 ICL. 112+0 also gives you a 112 ICL. Without changing the intake event's I don't really see much powerband change occuring...

Uh..... The previous cam had three degrees overlap, the new one has 9 degrees overlap. It's not advanced in timing for bottom end.

The previous cam should've come to 114 ICL and 112 on the exhaust. New cam is 112ICL and 108 on the exhaust.

The old cam definitely fell flat on its face at about 6,400, this one continually pulls to 6,800 without nosing over.

Hey and just a side note, you're part of dyno dynamics? I saw a YouTube promotion of you guys on what I believe was some Sick-Nasty Camaro. Cool stuff!

[eficalibrator]

Natural EGR just isn't friendly to fuel efficiency.

I would generally disagree. My experience has been that a slight increase in EGR improves fuel economy as long as everything else (ignition timing!) has been adjusted accordingly.

The added EGR displaces fresh air in the charge, requiring a slightly higher throttle angle in order to deliver the same relatively small aircharge necessary for the desired torque request from the driver. This means the engine operates at a higher blade angle and MAP value, but with the same MAF reading and fuel flow. This mechanism actually REDUCES pumping losses as the engine is not expending energy to create a vacuum in the intake manifold. Reduced losses generally lead to lower BSFC and better MPG on FTP test cycles.

Notice that I qualified this with "slight increase". There is a "hook curve" to added EGR vs fuel economy and it is often limited by engine roughness standards and misfire propensity. Too much EGR can lead to misfire, which is an excellent way to waste fuel if you don't burn it at all. The question then becomes "how much added EGR is too much?"

[DSteck]

You have to figure... I'm talking about the EGR from cams with a decent amount of overlap (enough to cause the lopey idle and noticeable change in drivability).

[LSxpwrdZ]

Uh..... The previous cam had three degrees overlap, the new one has 9 degrees overlap. It's not advanced in timing for bottom end.

The previous cam should've come to 114 ICL and 112 on the exhaust. New cam is 112ICL and 108 on the exhaust.

The old cam definitely fell flat on its face at about 6,400, this one continually pulls to 6,800 without nosing over.

Hey and just a side note, you're part of dyno dynamics? I saw a YouTube promotion of you guys on what I believe was some Sick-Nasty Camaro. Cool stuff!

Ah your intake valve events must have changed some then. Usually more overlap doesn't aid much in top end power but rather midrange torque.

I am not affiliated with Dyno Dynamics, but am friends with the guys that run the US branch. It is based in Lexington KY and I am actually located about 40mins from them in Harrodsburg KY. The only way I'm affiliated with them is I own a Dyno Dynamics that I tune car's on.

[IDRIVEAG8GT]

Ah your intake valve events must have changed some then. Usually more overlap doesn't aid much in top end power but rather midrange torque.

I am not affiliated with Dyno Dynamics, but am friends with the guys that run the US branch. It is based in Lexington KY and I am actually located about 40mins from them in Harrodsburg KY. The only way I'm affiliated with them is I own a Dyno Dynamics that I tune car's on.

Yup yup, all things considered, the cam drives fantastic with a 3,000 stall. I can lock the converter in 6th at 1,500rpm and it accelerates and bumbles around just as nicely as a stock car does.

On a side note, this cam requires about 4% more fuel thought the range of 3,000-6,200 and 6% from 6,200 up to the rev limiter. I'm in SERIOUS need of ID850's as my INJDC tops out at 129% where it was barely at 104% at 6,200 with the previous cam. Funny thing is, even with the additional overlap and lift I hardly lost any boost.

And I see! Well cool, next time I pass through KY I'll have to pop in and say hello. I do quite a bit of traveling out that way!