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Want to move to a smaller cam. Realistic expectations?
I've owned my 99 M6 SS for over 10 years and it has always remained stock. I recently purchased another 98 M6 Z28 from a member here that is far from stock with LS6 Heads, an MS4 cam, and related strengthening engine and drive train parts.
Said car's dyno is here:
I love the new car but am wanting to take steps towards taming it into a daily driver. This includes in a month or two looking into getting rid of the donkey dick MS4 cam and replacing it with what some might consider a baby cam. I've talked to EPS about what I might be looking for in a cam but have not decided on specs.
Here's the thing. I understand streetability and gas mileage is much more in the tune. I love efficiency. One of the most amazing things about the LS series of engines to me is that V8s with well over 300 and 400hp are capable of getting 30 mpg in some instances if you keep your foot out of it. The last thing I want is a place that will only tune based on WOT when 95% of the time, I'll be daily driving the car. Fuel mileage is EXTREMELY important to me to the point of where I am more than willing to leave power on the table in the tune if it picks me up a few mpg. Ideally, what I want is the absolute perfect balance between power and fuel mileage but I don't know what is realistic and what isn't. The car I bought gets about 22.5 mpg on the highway (with 4.10s). However, if I can get 25-26mpg (or more!) while only dropping 10 or so rwhp with the proper tune/cam, I gladly will.
TL, DR- I understand I need to be realistic but I am looking for a good tuner around SC that wont leave fuel mileage on the table and am looking at the best possible compromise between good mileage and power. The car I have dynoed at 441rwhp/385 ft/lbs tq with the MS4. Threads like this one-
make me think that I can stay in the same range of power and pick up a lot of gas mileage with the right tuner. Geoff recommended a possible 222/230 114 +2 cam. Is it possible to stay in the same power range with a cam of this spec? I asked Geoff but I didn't get a chance to forward the other parts in the engine until after business hours and he of course couldn't give me an accurate estimate without at least knowing those.
Well of course not. But the purpose of the thread is how much power I might lose. Whats realistic? 10rwhp loss? 20? And how much fuel mileage I might gain from that sacrifice.
Realistically with that you will be around 420whp so yes you will lose some. However you can go a little bigger than that and be just fine. A 226/230 on a 114 has 0 overlap and will still drive just fine.
Fuel mileage is hard to say but I would expect 2-3 mpg and have much better driveability
That is a huge intake port at 250cc, factory is in the 2teens. I'd relay that message to one of the site sponsors and have them spec you something with that in mind. They might be able to pull some valve event wizardry to help boost up the low and mid range power sacrificed with that big of a runner.
You need a complete different heads cam setup for what you want. I would sell the current heads/cam and have somebody like tony mamo spec you a new setup.
When I had my MS4, I absolutely hated it, maybe saw 150 miles to a tank with any sort of fun. Put in a crate LS6 with a Futral F13 on a 112 and was seeing over 100 miles more to the tank. I couldn't cruise without bucking with the MS4. You can still have a 230's duration cam and still have perfect drivability, also Kip had said he can grind EPS cams at any duration now so you don't have to go with one of his generic grinds. Just shoot him an email and talk to Geoff as well.
When I had my MS4, I absolutely hated it, maybe saw 150 miles to a tank with any sort of fun. Put in a crate LS6 with a Futral F13 on a 112 and was seeing over 100 miles more to the tank. I couldn't cruise without bucking with the MS4. You can still have a 230's duration cam and still have perfect drivability, also Kip had said he can grind EPS cams at any duration now so you don't have to go with one of his generic grinds. Just shoot him an email and talk to Geoff as well.
I guess the tune the car's tune isn't too terrible considering its running a larger throttle body than its tuned for. The car sounds half dead at idle but I only get bad bucking if I have it under 2,000 RPM.
19 degrees of overlap is going to buck no matter what under a certain RPM, no matter what they did LMR could never fix it, maybe pat G could have taken a couple more hundred RPM off the minimum RPM for the bucking, but even he said sometimes you can't do anything about it. Either way, I made more torque and more power throughout the RPM band with the ls6 and Futral cam, it could have easily been a 450/460 RWHP car with some ported casting from TEA/AI and a FAST, plenty for the street.
Want to move to a smaller cam. Realistic expectations?
Geoff specd my cam and it's only a 222/226 and the only other mods I have are stock 243 heads and fast 92/92tb and I put down 420/405 probably something little bigger than mine which he can probably spec out for you would put really close to what the car is doing
If you are really running an MS4 and 250cc heads with a 4.10 rear you are looking at a miracle car for MPG. Or it weighs 1800lb and is super slippery. 22 to 26 MPG is a bit of a jump. I'd look into getting the port volume verified and a mid 220's sized cam. Also look at going back to 3.73's
I'd consider ultimate streetability/MPG with more power a set of AFR 210 heads and a 225/227 114 ish cam. Obviously an opinion. I'll be running mamo 220's and the listed cam shortly for the exact reasons you are stating. My car has 4.10's and weights 3000 with me in it.
Stock casting heads will want a bigger split like EPS recommended.
IMO - think you will lose little more than 10rwhp at peak.
Your rwhp will be relatively the same up to 5000 rpm I bet.
However better gas mileage, driveability and throttle response are good trade offs.
If I have most of the same power up to 5,000 RPM I would be more than happy. I like not having to rev the **** out of the car to get most of the powerband.
He is correct those GM CNC LS6 heads are 250cc intake port and Huge! Not only that but the low and mid lift flow sucks per the size, and they have a Small bowl/valve size, those were like the first gm cnc heads for LS engines and you can make them better having someone tune the bowls,ssr and bigger valves but you still dont need a 250cc port, get some used ported 243's or maybe some TFS cast 220cc heads, or the PRC cast heads and you would be a lot happier!
Its all about the Efficiency of the combination!
07-11-2015, 04:58 PM
Want to move to a smaller cam. Realistic expectations? 
