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Old 07-10-2020, 11:13 PM   #1
cmitchell17

 
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What's Everyone's Grams per Cylinder?

I am thinking I went to big with my cam. Seems like there has been a lot of talk lately and kind of seems like bashing of the big vendors and them overhyping their cam specs. I kind of agree with this and it just seems like no one has a analytical approach to come up with a cam (or cam package with ported heads) that truly increases power. I mean I know they have to do some testing?

In my case I have a 228/236, .635/.635, 114-LSA, 111-ICL TSP Stage 1/2 that was "supposedly" customized between a stage 1 and 2. I also have their CNC head porting. I really regret not degreeing the cam when I installed it, but its just so hard when I have limited room and trying to get everything back together in a decent amount of time and not having all the right tools so I was being impatient. I also have a Pray earlier model ported intake and TB with a Rotofab dry.

I have seen some reports of people with stock Corvette LT1's reporting cylinder airmass over .90 grams. The highest I think I have seen is .88. The airmass profile compared to RPMs seems correct as it peaks around 5300-5400 as I would expect with my bigger cam, but I feel like I should have more airflow and something is wrong.

Since I didn't degree the cam I don't have a good way to calculate the intake valve closing and the dynamic compression ratio. I have a feeling if I could I would be greatly disappointed. Supposedly around .015 were taken off my stock heads and from that I am calculating I should be at maybe around 11.8 or so static?

I am thinking about a ported MSD, but they are just so expensive and they also I have non-stock look and are kind of ugly. I also have completely stock exhaust and stock headers besides a straight delete pipe for the AFM exhaust flap actuators.

Is there anyway I can find out about where I am with DCR? Also I set my shift points up just based on gut feeling at around 6850, but given how difficult it is to control consistent WOT shifts by changing the shift MPH, sometimes I end up hitting the limiter even though I have tried to cut out its aggressiveness. Anyone think I should be shifting it higher? Only reason I don't try it is I feel nervous going over 7000 as I have seen worries about the stock rod bolts above 6800rpms?

So maybe its the restrictive stock intake manifold? Maybe the stock head flow is stalling? My butt dyno indicated basically the same power after the cam and heads swap with a noticeably better top end above 5500rpms with no loss of low end torque. So I regret my cam decision and wish I still had some cam phaser authority (maybe 10 degrees) so I could help idle quality too maybe. I kind of wish I would have tried the GM hot cam and heads, or a cam motion cam like everyone recommends. I also really don't like the smell even though I have all stock exhaust and cats.
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Old 07-11-2020, 12:17 AM   #2
Tim M

 
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I'm unfamiliar with air mass grams per cylinder - I take it is a new parameter for tuning, etc.

Would a cranking compression not provide some insight into the engine's operating performance?

Also, you mention smell even with OEM cats. That seems you are saying it is rich mixture. I ran OEM cats with a pretty large cam at the time (GM 847) on a previous generation LT4 - was able to fine tune the MAF table with no smell and clean plugs. My idle speed was 775 rpm.

Cam info: I thought a cam card is included with all aftermarket cams, no? You could have taken it to a place with a 'Cam Doctor' to pull all the info...I know too late now.

What does it put out on the chassis dyno?
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Old 07-11-2020, 12:52 AM   #3
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so you have a head cam car on stock exhaust? ported stock intake manifold and rotofab...? street tuned it yourself, i presume?

sounds like you have a lot of issues contributing to poor performance.

edit: i can get you a cyl airmass value from my bolt on car this weekend. possibly when i get off work in the morning.
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Last edited by s346k; 07-11-2020 at 06:16 AM.
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Old 07-11-2020, 07:44 AM   #4
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I am FBO and E85 and see anywhere from .94-1.0 depending on weather...
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Old 07-11-2020, 10:32 AM   #5
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NA Heads/Cam setup won't make good power if it can not breathe. Stock IM and Exhaust is killing your performance. Headers (or at least primary cat deletes) and a ported MSD should pick up over 50hp on that setup.
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Old 07-11-2020, 10:35 AM   #6
cmitchell17

 
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Thanks for the feedback.

So "cylinder airmass" or "airmass per cylinder" has actual been called a few different things over the years between GEN III, IV, and V so its a little confusing. But basically it is supposedly the PCM "final say" on what it believes the true mass of air in the cylinder to be at that exact moment in time. My fuel trims from tuning myself are also within 5% and only about +/- 3% at idle, but I imagine at idle its difficult for the O2 feedback to work correctly given the high overlap cam.

I have to bump my idle speed up past 950rpm to get rid of the stumble and surge, but I kind of would rather live with the bad smell and vibration than have the car sound like its even more broken.

The cam card TSP gives doesn't include advertised duration, only duration @ .050.

Unfortunately I never got it dynoed and also never had a dyno of it stock.

I forgot to mention I am at 1000 ft above sea level and I notice a difference in baro of about .5 psi driving back to Florida.
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Old 07-11-2020, 11:03 AM   #7
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That cam shouldn't be that hard to tame being it only has 4 degrees of overlap. In my Fbody that I sold to a friend of mine, I ran a 224/228 112 that has around 5 degrees of overlap in a H/C LS1 and it behaves pretty well. That engine shows around .94 grams which is pretty strong for a little 346.
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Old 07-11-2020, 01:08 PM   #8
cmitchell17

 
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Quote:
Originally Posted by KingLT1 View Post
That cam shouldn't be that hard to tame being it only has 4 degrees of overlap. In my Fbody that I sold to a friend of mine, I ran a 224/228 112 that has around 5 degrees of overlap in a H/C LS1 and it behaves pretty well. That engine shows around .94 grams which is pretty strong for a little 346.
I tried to order some CA primary delete pipes but there website is apparently not working. I did email them though. I have seen the primary cat pipe restriction documented on here but has anyone ever actually flowed a set to verify how restrictive they really are? I am kind of worried that the smell will be even worse with the primary cats gone, but at least if it is real bad I can just unbolt these and put the cats back on. Working on exhaust is the most difficult and frustrating thing to work on so its important to have things that "bolt in" even though that doesn't always work given fitment issues.

I was surprised too to see that my cam only has 4 degrees of overlap which makes me question why there is so much noticeable lope and unburnt fuel smell.

When I was putting my cam in I did accidentally drop a socket down in the headers and ended up putting it back together. I ended up taking the pipe off again and taking it out but I did notice the cats had cracked, but not sure if this effected anything and weather or not it was the socket that cracked it, this is looking in from the band clamp end:
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Old 07-11-2020, 01:44 PM   #9
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Mass airflow is an indicator of VE, or induction efficiency, not energy conversion efficiency.

There’s a lot more to Energy conversion than mass air flow.
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Old 07-11-2020, 02:03 PM   #10
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I’m pretty sure these numbers can be skewed based on your tune so it’s not apples to apples.
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Old 07-11-2020, 02:30 PM   #11
cmitchell17

 
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Quote:
Originally Posted by gtfoxy View Post
Mass airflow is an indicator of VE, or induction efficiency, not energy conversion efficiency.

There’s a lot more to Energy conversion than mass air flow.
I agree, but with the way we are trying to make more power with mods that either free up airflow restriction or "tune" the engine to resonate at a higher RPM.

If I put in a cam and airmass per cylinder did not increase, it did me no good, but I agree too that combustion efficiency plays a part too (tune, compression, etc.)

I like to put my trust in the factory air metering system (mainly the MAF sensor), as long as you don't go and hack it up, more than I trust someone else randomly using a unknown-calibrated dyno with random parts and not being able to verify in person. I would trust a flow bench over a dyno as well. But unfortunately I know we don't have a choice and have to trust it since we all don't have millions of dollars to put into our own research lab haha
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Old 07-11-2020, 02:32 PM   #12
cmitchell17

 
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Quote:
Originally Posted by 6spdhyperblue View Post
I’m pretty sure these numbers can be skewed based on your tune so it’s not apples to apples.
Yes you are right, without a correct airflow model. However, with someone with a stock air intake on stock MAF with a stock MAF calibration, I don't see why it wouldn't be accurate enough to pick up increases. The rotofab is supposedly supposed to work on the stock calibration. Thanks for the numbers
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Old 07-11-2020, 02:33 PM   #13
cmitchell17

 
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Yes you are right, without a correct airflow model. However, with someone with a stock air intake on stock MAF with a stock MAF calibration, I don't see why it wouldn't be accurate enough to pick up increases. The rotofab is supposedly supposed to work on the stock calibration.

Thanks for the numbers, it seems like I am way lower than everyone else.
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Old 07-11-2020, 02:53 PM   #14
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My screenshot numbers aren’t off a stock car. Fyi

I know you’ve been looking for ideas with you car here and hptuners.

https://forum.hptuners.com/showthrea...or-Calibration

If I were you I would open the tune in this post and copy the following:
vve, dd tables, virtual torque, the pedal torque rate limit tables(keep the stationary one to disable), idle tables, peak torque, maybe even the timing table if yours isn’t zerod in. I would not use the PE. Set your cam phasers to NONE as it is in this tune.

Zero in your fueling with maf and see What it does. If it’s not bad I would say work toward tailoring you vve starting with this table. After it’s perfect, I bet it will look different than what you have now. It worth a shot to see If it makes an improvement for ya
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Last edited by 6spdhyperblue; 07-11-2020 at 05:46 PM. Reason: Forgot the idle tables
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