Here you go Steve: https://www.avl.com/pressure-sensors...stion-analysis

 

And if you want to buy the entire measurement and logging system:
http://www.tfxengine.com/index.html

High end engine dynamometers will have such a system to measure the pressure in each cylinder, the exhaust temperature of each cylinder and much more.

 

You and I both. That data graph is a fascinating visualization of the dance between pressure waves and valve timing.

 

Do want.

 

Thank you Martin! Just read through this thread after reading through the SNS cam thread. Some good info that I definitely didn’t know. Glad that you showed the graphs……that definitely put a picture to the words to make sure it all stuck. I had read through another thread where you were talking about the difference between camming an LS1 and a 5.3 motor. You were saying that some people’s perception of needing to use 15 degrees LESS of duration in camming a truck motor was not the same opinion as yours. Could you talk about that a bit here if you have some time…….It seems like if both motors had he SAME compression their only difference would be the bore. This would mean that the stroke and piston speeds would be the same if they were used in the exact same operating RPMs. That I can see going in line with your opinion. My question is when you compare an LS1’s compression to a dished piston 5.3 (LM7) with less compression………how do you compensate for that less compression when you design a cam. It seems like the best thing to do would be to mill the heads and make the 5.3 have the same compression as the LS1, but a lot of the truck guys can only afford to do the simple bolt ons and a cam. The truck engine does have the truck manifold on it with different runner lengths/size…..and like you said this can change a LOT of the motor’s charactoristics. The 706 heads and the 241 heads flow pretty close to each other….can’t remember about runner length or volume of the two against each other….buuuut I’m sure someone can reply with that info to make sure we stay on track with facts. The lower compression 5.3 seems to be the source of a decent amount of threads where cams brought up that are over 220/220 get constantly shunned or shot down as being way too large for a truck motor. I know that a truck weighs 4300 pounds, but we are just talking about the two engines (LS1 vs LM7) in general. If you have some time and want to continue on with a bit of compression talk……I think a lot of people would benefit from using the truck 5.3 engines in your examples because of how readily available they are for cheap, and how most of the information about camming them comes from the truck forums where cam info isn’t discussed to this length. It seems like a lot of people are stuck on 220-224-ish cams on the PT forum while another forum from a valley in Texas has people running cams routinely 8-12 degrees more of duration in the same vehicles with the same stall speeds and having some success at the track. Thanks again for the awesome education……I’m a truck guy learning as much as I can here….LOL

 

I have since started to cam 5.3's a bit differently than I used to. I have experimented with smaller cam grinds in 5.3's especially in heavier trucks and SUV's with great success.

Even though the piston speed is identical and even though piston position is identical, swept volume is not. The amount of volume we have to fill the cylinder is smaller and as you pointed out as well the compression is lower.

Because of the swept volume being less and cylinder pressure being lower, one must close the intake valve earlier and open the exhaust valve later to retain as much useful cylinder pressure as possible and to maximize torque. I now feel that a lot of people over cam 5.3 engines and especially so in trucks.

IMO to successfully run a 224/228 duration cam in a 5.3 truck you would need at least a 3600 stall and 4.10 gears. Some of these 228R and 228/232 cammed trucks need a 4000 stall and 4.56 gears IMO.

I have several smaller 213/217, 215/215, 215/219, 217/221 and 219/223 cams I use in trucks with great success. I get a lot of customers that call me and say, "My buddy just bought a cam from you for his 5.3 truck and he's blowing my doors off, but I have a bigger cam and make more power on the dyno."

That seems to be at least for me a reoccurring theme lately. Even with 5.3's in general and not just in trucks. I have a lot of customers with 5.3 swaps in 5.0 Fox Body Mustangs that spray 150-250hp worth of nitrous. None of those cams are over 229 intake duration and all of those cars run 9.60's-10.20's in the 1/4 mile respectively. I've re-cammed several 5.3 engines in Fox Body Mustangs and G-bodies that have picked up very well over their previous larger camshaft.

 

I have been reading this entire thread and thanks so much for helping me understand cams. Martin I think you have hit on something with the 5.3 cams needing to be smaller in duration, it just all makes sense

 

Cool info Martin. Thanks for explaining that. I kept seeing people on the cheap take the low compression 5.3 motors, mill the heads to up the compression to about 10:1 and then stick something like a 228R in it. Can that bump in compression actually make up for this lack of physically swept volume? Can that power band lowered or extended down to actually be used with say a 3200 stall and 4:10's by milling the heads to create about the same compression as an LS1? I was talking with someone the other day about how much you would have to mill some heads on a low compression 5.3 to ge able to use a larger duration (224-228 duration cam on like a 110 LSA) with a more streetable stall like a 3200 and some 4:10's. Do you think that is possible to shift that power band down THAT far with milling the stock heads to get 10:1 out of it? Seems like you could do that if you yanked the heads and swapped over the lifters anyways if you had a few extra bucks.
I see the guys on RGV rnning pretty big stalls for a truck on the street like you were saying....LOL....4:56's and a 4000 stall.....in work truck.
If you could mill to get the compression to 10:1, would the now smaller combustion chamber combined with a dished piston need an odd sized cam because of the now different "shape" of the combustion chamber combined with the piston as the mixtre is started to get squeezed or the cylinder is filled?
My buddy and I have been talking about ways to keep the low compression 5.3 SHORT block in the truck and put a short bed SOLID into the 12's with a truck intake manifold, 3200 stall, 4:10's, and the usual bolt on's. It seems like if you went to swap the lifters and pulled the heads you would be swapping the springs out anyways.....so that is why I brought up the milling of the heads as an idea or discssion with you.........
Thanks again for the insight into all of this....I know a LOT of people will read all of this and learn a lot from what is talked about throughout this thread....as we talk about it....or as people join the site in the futre.....that is one reason why I am talking about milling the heads on the low compression 5.3.....they are fairly cheap and there are a TON of them out there for guys to built cheap street machines in the future!

 

Hey martin, great information!

I have a pretty specific question regarding cam overlap.

I have a bone stock ls1 daily driver. I'm not interested in horsepower gains (yet due to lack of $$$), but i am interested in sound (and driveability).

I really like the nice choppy idle of the GM Hot Cam. So, based on what you've told me here, all I have to do to get that sound is find a cam that has the same overlap, right?

My stock cam has .500 lift on both sides, if i were to purchase a new custom cam with the same .500 lift but with duration such that i achieve the same overlap as the Hot Cam, can i safely run it with my stock valvetrain? (Since i'm not increasing lift, my pushrods will be at the same length and the springs will be at the same spring rate, right?)

If i were to do this, would my driveability be completely destroyed or would it be suitable for daily driving? (I realize the power band will be shifted) Thanks!

 

LSA matters when it comes to PTV clearance.

 

Adding compression cannot make up for a loss of swept volume. It can help with cylinder pressure and torque production, but that is it. You could then use that added cylinder pressure combined with the right valve events to manipulate the power curve somewhat, but it still cannot make up for volume.

That is correct, if you grind a cam that has the same amount of overlap(or very close) the sound you're attempting to match from the Hot Cam should be created. Obviously tuning, exhaust design and exhaust manufacturer can play a part in sound at idle, but overlap is mainly the deciding factor.

I have done a few "drop in cams" where customers used the stock push rods with beehive valve springs for a cheap and easy cam swap that nets very respectable results. You could do the same with a mild lobe design. You may even be able to get away with a LS6/LS3 style valve spring if the ramp rate of the lobe is mild enough.

That said, I would not automatically assume that the stock push rods will be the correct length even if the lift is the same and that the stock springs will be able to control the lobes. Lift is not the sole determining factor in how aggressive the ramp rate of a lobe is.

LSA= ICL+ECL/2

ICL and ECL matters when it comes to PTV clearance. Not LSA.

 

Kind of a trick bag isn't it? LOL

LSA, ICL ECL and duration are all just mathematical expressions of the relationship of IVO, IVC, EVO and EVC to one another.

So, as Martin so wisely pointed out to me some time ago, valve events are the clearest picture of what is going on.

If I want to figure piston-to-valve, I want to first know the valve drop measurement, then I want to calculate the proposed IVO and EVC.

 

Novice question here.
How or does altitude affect or influence valve events? Does it change your approach?
I'm at 6500ft, and say you had a customer with an identical setup at sea level. Are any changes in In valve events needed between the two? Hopefully that makes sense lol

 

Idk if it changes valve events just know there is less oxygen in the air and it's thinner so you will run slower. Btw where are you at?

 

I'm about an hour south of Denver. Ya the altitude is a killer it seems. stock48 makes it look so easy though lol

 

Lol i bet but he probably has a lot more money in his set up than you idk. Either way Martin will chime in when he gets a chance to fully answer your question. This is a great thread for sure.

 

Didn't think it needed to be said, but OK.

 

Higher DA to me means less cylinder pressure.

This is due to a reduction in air mass which means a reduction in pressure once that air mass is trapped in the cylinder and compressed.

To combat this I shorten the duration of the camshaft by closing the intake valve earlier, and opening the exhaust valve later.

I try to preserve as much cylinder pressure as possible and utilize that pressure as much as possible since in this instance pressure will be limited due to higher DA.

We don't want to incur a pumping loss by closing the intake valve too soon, or opening the exhaust valve too late and not evacuating all of the spent exhaust gas, but like any camshaft it's a balancing act.

When you look in the comp cams lobe book(or any companies lobe book for that matter), are the tappet lift figures for TDC listed based on LSA? Or are they listed based on lobe centers?

 

Great post, very informational.

 

Great info, i learned alot