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New Cams, now sucking fuel like a cheap ****

Bass Junky

By Bass Junky,
in Victoria

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Bass Junky Grand Master

Bass Junky

Posted
Posted

Hey guys and gals.

With the new Cams, my car is sucking the juice like you wouldn't believe.

I got 410 highway kilometers on a trip to Albury and back recently.

I think my cruise ratios are at about 13.2:1

What is ideal, and what other things could be effecting my fuel economy?

I've only recently changed my oxy sensor.

BASS OUT

paulr33 Grand Master

paulr33

Posted
Posted

what city driving like? im happy with 400+ odd kms from highway driving

my r33 sits on 2800ish all the time at 100km/h so 400km's is resonable in my car on highway.

city driving i get around 320km ish to a full tank. i dont let it run empty or wait for light, one the needle is on the low line i fill up. im assuming youve made sure 02 feedback is on and what is the value for 02 under sensor check like at idle. its a shame you can't monitor 02 under monitor and plot it on graph, would be handy. strange that cams would have such a drastic effect on fuel economy?

Abo Bob Grand Master

Abo Bob

Posted
Posted

I get about that many k's. Get us some L/100Km figures and then we can make a better judgment. For all we know you could be filling up 40L instead of 50-55.

I've also got a consult cable which connects to my laptop and logs just like paul is saying.

I recall SK saying that with cams it can make the car run rich in the mid range so maybe since that's where you spend all your time driving...

Also, has your idle been raised slightly compensate for roughness induced by the cams? Only a couple of hundred rpm can have a huge impact on fuel use.

WetGTR Proficient

WetGTR

Posted
Posted
I've been told that with reasonable size cams, that 14.7 is far too lean....

You burn exhaust valves.

Is this correct?

Depends on how big your cams are.

SK has said in a previous post that too lean a mixture even 14.7 for big cams will burn out your exhaust values. I spoke to my tuner about this and its true, also you would be lucky if the engine would even take that ratio without surging.

Best to get a tune first when ever you make any mod that will change the volumetric effiency of an engine. Cams fit this category for sure!

Another thing: cruise ratio's of 13.2:1 is running on the rich side. In Closed Loop you should be able to run the 14.7:1 ratio or even leaner but depends on cam sizes.

What are your new cam sizes BTW?

WetGTR Proficient

WetGTR

Posted
Posted
Cams are Poncams, 260 degree by 9.15 lift.

So you said that 14.7 would burn valves, but you also said that in closed loop I can run 14.7.....

What say you?

Yes I said this but for BIG cams like 280 degree or maybe even the 272.

The cams you have fit in the MID type range with a lift on the small side. These are a great cam and I'm getting a set myself but with 10.25 lift as I have that lift in my cams ATM.

In closed loop it aims for 14.7 in light city driving & 14.7 or leaner if your ECU is capable - leaner mixtures for economy.

I'm changes my cams for this exact reason, I can't go any leaner around 13.1:1 because it will surge or its too lean for my exhaust values and they would burn out.

With a tune they would be able to see what AFR you are able to run across all load & rpm points to suit your cams then setup your closed loop.

WetGTR Proficient

WetGTR

Posted
Posted
How do I do this with the Power FC?

This has to be done on the Dyno with a wide band UEGO sensor for your AFR. With this information they can set the fuel delivery maps. If you have adjustable cams gears, they will be able to set these for your new cams as well.

The timing has to be set as well for load & rpm points.

Another thing is these cams should give you more power if this was an upgrade so getting it tuned = more economy & power....hmmm nice combo.

Always use a reputable tuner though, no good having the right stuff and someone not setting it right = waste!

WetGTR Proficient

WetGTR

Posted
Posted
These cams actually cost me power!

Check out my other thread about it!

OK, interesting read!

I agree with SK, Installing bigger cams means you are allowing more air & fuel to be let in per cycle - less restrictions but in your case you can get the fuel there in the right quanity but run out of air, re your stock turbo. A high flow, GCG or something bigger then your stock will fix this for sure. You would of noticed the difference when you turned up the boost - right? Well wait till you see the difference with a high flow or bigger turbo....wow factor!

Also, talking to Benno (Racepace) will confirm or change what needs to be done. I also believe (without knocking anybody) he is the tuner thats ends all tuners. Wish he was here in sunny Queensland. Trying to convice him, hahahaha.

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