Especially with wide LSA cams which fly in the face of DV’s experience.
Torque = Driveability ? (Engine Masters LSA shootout)
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Especially with wide LSA cams which fly in the face of DV’s experience.
So that is not what DV has told Comp when he did those 1000 tests for them. He vents a lot about cam companies that tell people the opposite of what he has showed them with data.
DV's choice is vary similar to 3rd place cam spec's and his intake points are similar to 1st place but very different from the other 3 in the top 5.
It's quite clear this engine didn't need a lot of intake duration compared to exhaust other the 1st place getting there with a wide duration spread, the others seemed to get a piece of it either intake or exhaust and made it up in other ways like LSA.
I just ran two cams that he gave the LSA/ICL and it centers the overlap triangle, just like I said.
Sadly, too much information is missing. Like the seat to seat timing and the ICL for most of the cams. And lift.
Nobody cares about the at .050 lift over lap.
I'm not sure what your saying, are you saying Comp Cams break down that Kern Dog posted is wrong or that they stole it from DV ?
If you saying they stole (didn't give credit) that break down, it's been common knowledge far as I can remember back (80's) No one else ever notice that trend before him ?
He worked for them (and others) testing 1000s of dyno runs and what they suggest typically does not agree with his results.
PRH
Well-Known Member
Funny stuff……
“my cam guy is better than your cam guy”
“my cam guy is better than your cam guy”
My guess cause they don't want to stock a infinite amount cams with all the various possible LSA's. It's easier to offer one to a few LSA's, imagine the seven or so cams available in the XE line if were available just not just 110 lsa (which is probably close enough for most) but every half degree from 100 to 115 or more on either side never mind all the other lines of cams.
That is the exact reason. Here is what we have so it gonna be what you need.
Funny stuff……
“my cam guy is better than your cam guy”
Exactly, as I said earlier the cam profile is an OUTPUT of at least half a dozen other decisions you make in the build first!
I can barely understand cam science and now I read someone added "Triangles" to the conversation?
I have not read all of the responses in this thread. Much of it went way over my head and will never apply to a guy like me that just wants a streetable fast car without chasing the last bit of power.
The dyno tests on the Engine Masters episode do seem to be weird. They all make similar HP but different torque numbers ?
I had a 440/493 with a MP '509, a Comp XE285HL, a Lunati 316/326 and a MP '528 solid. That is a fairly wide range of cam designs for me. The 528 made the most power down low and had the best idle vacuum despite having the widest LSA. The Lunati has a 106 LSA but makes the most of it's power from 3000 rpms and above.
I am far from an "expert" engine builder. I can assemble and tune a bit but the science discussed in this thread goes WAY beyond what I'll ever do.
I'm switching to a hydraulic roller with a 112 LSA to have better idle vacuum but I expect it to be peaking well under 6000 rpms whereas the Lunati I have now keeps pulling hard at that point.
PRH
Well-Known Member
Imo, With hot street cars its all about finding the best balance of compromises for a particular combo/owner.
The same build might get noticeably different cams based on the vehicle usage and owner preferences.
The same build might get noticeably different cams based on the vehicle usage and owner preferences.
Absolutely.
If I had an automatic and manual brakes, the higher peak HP from the Lunati would be fine....and fun.
I have a Tremec that doesn't like to shift above 6000 rpms and I have power brakes so a cam that peaks below 6000 rpms is a better fit for me.
The Lunati would make a faster drag car if I were into that.
I'm not.
BSB67
Well-Known Member
Okay. Thanks.
Kinda hard to follow with what was, verses what it will be. My questions were pretty simple but hey, we all like to talk about our stuff.
The ET and MPH are kinda important for the purpose of understanding and perspective in your responses to the OP and your credibility considering your statements of authority. But you have no ET or MPH because your motor ate itself. Maybe next time.
Anyways, the OP asked about "drivability" and "low speed torque". Honestly, I don't know what he's asking or what's important to him. I have no idea why torque at cruise rpm or at some predetermined rpm is important to people. I simply prefer my cars to be fast and nice drivers. But I offer this regarding your comments: maybe your 4.88 geared, dual quad, manual transmission car with a 255 @ 0.050" is not considered to be "drivable" by everyone just because you think it is and you can drive it. It is an opinion. And it's not fixed by tuning, only made worse with poor tuning.
I'm not found of the term "drivability". For me it's driving "manners". As an example, I prefer +14" vacuum at idle and tighter converters. Don't care about torque at cruise - it has enough. My last cam change took me from 14" to 15" of vacuum at idle. But that's me, I don't expect anyone else to have the same opinions/goals. Likewise, they may not share your idea of drivability either.
In the end, cam choice in a street car is a compromise. Where an individual is at in terms of "drivability" or "manners" will decide how much they should move in one direction, or the other regarding cam timing and LSA.
Anytime someone wants to build a 318 (small cid) for example or even a cam swap or intake swap etc.. every time low speed torque and it's supposed effects on driveability comes up and as I see more and more dyno results I'm not seeing this correlation between the two or at least a strong one.
Why I created this thread the LSA test kind of contradicted two assumptions I see a lot, I feel most would say that tighter lsa would give up driveability but the contradiction is it also makes more low/mid range torque which goes against the idea low speed torque equals driveability, I posted it cause I found the contradiction amusing
100% but probably most would consider driveability equal to street manners.
Question is does torque at 1500-3000 or so rpms have a huge effect on driveability/street manners etc.. ?
You made an assumption. You’ve never driven my car, so you can’t possible know what it’s like.
The car with the engine in when I bought it (it had the cam that is one step smaller than the 284/484 hydraulic and for the life of me I can’t remember the exact cam but that’s what it was) would go 12.5x-12.7x depending on conditions and who was driving it. At that time it had a Strip Dominator, Hooker 5204 headers, an 830 Holley that was absolute junk and 9.2:1 compression. It was running close to 110 MPH but it needed shock help.
He was looking at shocks, but he died so that’s how I ended up with the car.
His wife could drive the car in the low 13’s. It was drivable. I posted the above because those are the changes I made to it, and it will drive very easy.
It won’t buck, shuck and jive or anything else. It will start easily on sub freezing days and won’t overheat on 100 plus degree summer days.
It will idle easily down to 750 but I don’t let it.
Again, your assumption that my car isnt “drivable” because it doesn’t have 14 inches of vacuum at idle is just your assumption.
And it will be slightly over 12:1 on pump gas and won’t rattle. 90% of the guys on the forum would say Thats not only not driveable but it’s not even streetable.
Of course, they are wrong.
Anytime someone wants to build a 318 (small cid) for example or even a cam swap or intake swap etc.. every time low speed torque and it's supposed effects on driveability comes up and as I see more and more dyno results I'm not seeing this correlation between the two or at least a strong one.
Why I created this thread the LSA test kind of contradicted two assumptions I see a lot, I feel most would say that tighter lsa would give up driveability but the contradiction is it also makes more low/mid range torque which goes against the idea low speed torque equals driveability, I posted it cause I found the contradiction amusing
100% but probably most would consider driveability equal to street manners.
Question is does torque at 1500-3000 or so rpms have a huge effect on driveability/street manners etc.. ?
That’s a good point about low speed torque. The assumption is you need 500 foot pounds of torque or it’s a slug. That is entirely not the case.
Street manners is really what counts but there will never be consensus on that either, because of all the assumptions made.
Streetablity is at least 90% tuning and that’s just the truth. Most guys won’t learn about what tuning really is or what it takes to tune.
So of course they turn to the internet where rumor, innuendo and general misunderstanding is passed on like the clap in a high school football locker room.
Terms like “Holleyitius” are coined and used because they’ve never overcome the bad tuning strategy that has been handed down for decades.
If you say get the engine on a dyno they scream bloody murder and it costs too much. And my favorite nonsense line is “I don’t know why they don’t pull the engine down to 1500 rpm where these street engines spend most of their time” crapola.
That comes from zero experience with a dyno and zero knowledge of how you can tune with one. Some of that is the fault of the dyno owner and some of that is the customer, especially when the customer just wants to make acceleration tests without regard to developing a timing curve, sorting out the carb at different loads and RPM or deceleration testing.
All are valid test strategies for specific purposes. And there are more.
You can never get guys who have the bias of certain parameters must be met (idle vacuum, which is a concern with power brakes but you can work around that, and several other “standards” for “street ability”) to think that maybe they don’t know what they don’t know.
BSB67
Well-Known Member
I've owned and been in a lot of cars with 70-100 overlap cams. In fact, I own another one now. I believe that you are the one that has made an assumption - that you are the only person that knows how to tune an ignition and carburator.
You need to go back and re-read. Neither of those are my assumptions. I did not say your car was not drivable. What I said is that what you think is drivable might not meet other peoples definition of drivable. Drivability is an opinion. Neither my opinion nor you opinion are right or wrong.
You seem to want to provoke an arguement with this statement, as you have said it a couple of time without anyone asking. Do us a favor though: When it is put together, post the final actual CR and the cranking cylinder pressure. That would be useful data.
BSB67
Well-Known Member
Now that is an unfounded assumption if it is directed to me.
I’m certainly not the only one who can tune a carb and an ignition.
I learn new things every day. But here is a fact for you. You can verify it on this site very easily.
You have people on here who through simple ignorance (meaning they don’t know because they’ve never been taught…that would be me at many points and I own up to it) and you have some on here who perpetuate (continually) simple carburation tuning errors because they either refuse to learn, won’t test for fear they will be wrong or both.
I watch certain guys on YouTube who have plenty of subscribers (I could name them but it doesn’t really matter) who claim to be expert tuners and they have no idea how the MAB functions and how the emulsion circuit works.
I’m in contact with some of the best tuners in the country, not because I’m special but because I network very well. If I run into an issue, I don’t go the interweb for information, I get on the phone.
I have learned an incredible amount about ignition timing since I was called out on Moparts in 2017 I think. In fact, the guy who called me out is one of the guys I call for help and to get my stuff straight.
He exposed me so bad that I publically apologized to him on the forum AND I went out and bought a distributor test bench so I could verify exactly what I was doing.
In 2020 I bought the dyno. That has been a MASSIVE learning curve on several levels. It’s one thing to go and run a dyno which I have done plenty, but it’s a whole different thing when you OWN it.
That tool has steepened my learning curve on timing and carburation like you can’t imagine. And I have three very good mentors who help me not only with tuning but with testing procedures and such. One of them I won’t mention but he was the head of dyno testing for a US Auto manufacturer.
I don’t just say **** without having done the testing first.
Drivability is an opinion, but it is also quantifiable. Someone in this thread (I think) tried to claim his friends 6 second dragster would be drivable according to my understanding. That is a gross error.
For one, a 200 inch plus dragster can’t turn a corner. It won’t have enough cooling system to go very far. It won’t hold much fuel. So by definition it’s not STREETABLE. Certainly you could drive it some on the street, but not very well.
OTOH, look at the drag and drive cars. I’m not talking about the 5 and 6 second cars, but some of the low 8 second to high 9 second cars. Especially the stick cars. Very streetable and drivable.
I’m not trying to provoke an argument when discussing my compression ratio. YOU asked ME about the details of MY car, so I told you everything I could.
I have been running higher than orthodox compression ratios since 1981. I never bought into the X.XX compression is all you can use on pump gas because it’s not true. That’s why I talk about it all the time.
The number ONE reason most of the cars with a lot of overlap (how much a lot is is of course an opinion) run like sour owl **** is because they use way more cam than their compression ratio allows. You can half *** tune around it, but the correct fix is to up the compression (the best fix IMO) or run a smaller cam.
I was waiting on my cam. It showed up two days before my mom got sick. I’ll probably not be home for another 6-7 days. I’ll go back to work on my engine when I get home.
But, I have other engines on the schedule to dyno and that comes first. It will go across the dyno and I will publish the results.
Myths, fairy tales and outright lies live long lives. Truth has to overcome the inertia of all that. And it’s hard for truth to get any traction when the purveyors of the above will fight to the death to defend the error.
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That wasn’t directed at you. If you must have power brakes then you (not you specifically but you in the general sense) have to live with your choice.
You can not make as much power if you are cam limited because that cam limit to run power brakes limits how much compression you can run.
Compression is power across the entire curve.
Are you running the Lunati 251/251 .570 solid on 105lsa by any chance?
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