Unequal camshaft duration 4AGE

[DeftAnesthetik]

to me an engine is just a mechanical air pump, to be optimised by changing different parameters, and understanding those parameters is interesting

....you do the hokey pokey and turn yourself around, thats what its all about

you would be surprised at how many people don't understand thats all an engine really is!

[Billzilla]

....you do the hokey pokey and turn yourself around, thats what its all about

you would be surprised at how many people don't understand thats all an engine really is!

*sigh*
Small but bloody obvious secret time.
When it starts to get hard to get more power from the engine, it's (past) time to look at reducing losses, both frictional and pumping, of all fluids.
There's a surprising amount of power in that.

[brett_celicacoupe]

it's (past) time to look at reducing losses, both frictional and pumping, of all fluids.
There's a surprising amount of power in that.

coates engine FTW!!


http://www.coatesengine.com/technology.html

[Billzilla]

coates engine FTW!!


http://www.coatesengine.com/technology.html

Pffffft .... the Aussie Bishop rotary valve FTW!
http://www.squirrelpf.com/articles/AutoTechBRV.pdf

Came this close (hold your fingers a small distance apart) to being tested in the back of an F1 car a few years ago.

[oldcorollas]

*sigh*
Small but bloody obvious secret time.
When it starts to get hard to get more power from the engine, it's (past) time to look at reducing losses, both frictional and pumping, of all fluids.
There's a surprising amount of power in that.

for sure.. which is what toyota have been doing in engines from gen to gen...
(people wonder why the 4AG rods got lighter?)
Ti valves, half back cut cam lobe base circle etc... (there is a good paper out from toyota about losses of cam drive arrangements with losses for each)

Bill, was it that or the coates that was actually built into an engine (and installed in formula car..)??

[Billzilla]

for sure.. which is what toyota have been doing in engines from gen to gen...
(people wonder why the 4AG rods got lighter?)
Ti valves, half back cut cam lobe base circle etc... (there is a good paper out from toyota about losses of cam drive arrangements with losses for each)

Bill, was it that or the coates that was actually built into an engine (and installed in formula car..)??

Niether. The only application I know of that used the rotary valve head was old man Clisby (yes, the guy that made air-compressors) in South Australia in the 1960's. He built a rotary valve head for a Holden straight-6 and put it in a hydroplane. It used to thrash Chevy small-blocks.
I haven't ever been able to find out any more into than that sorry.

[DigitalPho3nix]

Sorry to dig this thread up!

Thinking of getting a car that has a silvertop 20 valve in it.

Since the 20v has 3 inlet and only 2 exhaust ports, I am assuming it would be well worth getting a larger duration cam on the exhaust side EVEN IF you don't bother changing the intake cam? It has 3 intake valves per cylinder and individual throttles after all... That's alot of gas flow there already.

I am only chasing some small top end power gains since this engine is in a really small, light car.

[Talasas]

Okay, yet another thread dig. I have read through all of this and many tech articles and feel even less educated and more confused than I was before I started.

Here is my situation:

- Smallport 4AGTE got upgraded with many new bits, including a new turbo (TD04L). More or less a simple setup, short cooler piping, sensible intake.
- I'm currently setting the valve clearances as they are out and I need new shims.
- I have a set of Bigport cams on hand, the exhaust cam has 1 chipped tooth on the dizzy drive gear ( )
- The engine needs a dyno tune anyway

So while I'm here, I'm considering putting in just the intake cam - can I conclude from all this discussion I'll need to experiment to find out if I'll gain anything? I thought while I'm pondering my options
I'd ask for some feedback. At risk of sounding like a n00bah, which of these seem like a good path to head down?

1: Bigport intake cam, Smallport Exhaust cam
2: Leave the Smallport cams as they are
3: Get the Bigport exhaust cam repaired and run both Bigport cams

My understanding says bigger lift with some longer duration allows more air in and sooner, that's pretty vague however. What I'd like to get is more bottom end torque if it's available.

If anyone wants more details for their reasoning just ask.

[nick.parker]

I'd suggest that since bigport cams are still so mild use them for both intake and exhaust.
After using the following combos in my 18psi SC14'd AW11

240in,240ex (stock) massive low end, asthmatic from upper mid revs
240in, 267ex, (stock + wade) weaker bottom end, mid ok, less torque drop off at revs
267in,267ex, (wade cams) weak low end, GREAT mid range, top end as good as it gets
256in,267ex, (HKS + wade) low end ok, mid very good, top ok
256in,240ex (HKS + stock) big low end, big mid range, top end ok

I can say that the last combo (256in+240ex) is the best I have yet tried for increased mid range ability with little low end torque loss. Basically you wont get much better drivability than stock cams for the SC'd car! Better to get more lift, ported head, better intake and exhaust, maybe more compression than fit large duration cams! Of course yet can reduce overlap with big cams by retarding the ex cam etc to help fix idle and low end a bit but this always seems to screw the mid and upper rpm performance of the bigger cams.

I might add I haven't tried the combo like Adsports 264in 256ex (with what I have that would be 267,256).

Nick

[Cameron_Datto]

What lobe Centres are dialing the cams in at ? or are just putting them in without checking them ? 110 deg on the inlet cam and 116-118 deg on the exhaust on wade 267 deg cams work good for a broad strong mid range

[Talasas]

Cheers guys, I think I might get a quote on repairing that cam tooth and see how I go.

[YoShImUrA]

Hi, after lurking for years and gaining a lot of info from reading up on this forum, I'm finally posting for the first time.

I'm having a bit of a dilemma with what cams to use on my 20v blacktop engine.

First, it's got 100mm SQ-engineering velocity stacks (no air filter at the track, which steals about 7hp on dyno), "cleaned up" intake ports, 11.6 CR, 81mm Toda forged pistons, forged MaxSpeeding rods (much better quality than their name or provenance would make you believe), Toda valve springs, lightly ported exhaust ports, K1/pass racing headers, COP conversion. and a Microtech LT-9c standalone ECU...

I first installed Tomei poncams (264 in 256 ex 9mm both) and the car made 142 whp at 7000, with 123 ftlb (167 Nm) @5k RPM to the wheels (remember, still a 1.587cc!) on a dynojet. Low and mid range was like driving a good 2.0l, but I really wanted more on high RPM for the track, where I use it the most. If only I had been building it for a rally car...

So then I fitted a pair of TODA 272 9.2mm. I installed both cams with the pins that allow for the 5deg difference these cams require (they were initially made for the 20v Silvertop), and no, I didn't use adjustable cam gears, as I couldn't afford it at the time and part of me wants to keep VVT for drivability on the road.

On the dyno I first went about dialing in the ignition (I had already street tuned the fueling) and after this I updated the VVT activation from the stock RPM range in the Tomeis, to basically full open on the TODAS. I looked at everything possible to optimize them on my tune (duh!), even by trying a different catback to see any difference (from a 60mm Brave, to a 60mm HKS Hi Power) but I couldn't get anything else out of it.

In the end it had loss up to 15 ftlb in the low and mid range. until they became identical downward slope after 6500 RPM. So, 140 whp at 7500 and 113 ftlb (154 Nm) at 6500 RPM. Same dynojet, but a much hotter day too, from 23C to 39C, which could have been a factor, but not that much, I think.

In retrospect, I wonder if I was running ignition too high (up to 40deg), heating up the engine excessively, but crucially killing power (we had constant pre-ignition monitoring and it never gave any signs of it below 42 deg). No, we didn't have a rolling bearing dyno to find MBT, only inertial. So we reached this ignition tune by doing short dyno runs on a certain RPM range (eg: started from 3-5000 RPM, 4-6. 5-7, etc., and went on and on, and finally double check with full 3k to redline) to find a good ignition value. But I think I need to optimize and test the ignition further. Maybe just doing full runs and just changing 2 deg at a time. In the end and still today, I'm quite puzzled why both cams were limited in exactly the same way after 7k.

Now I have both pairs of cams, and I'm wondering if I fit the Tomei 264 9mm on the intake (with the TODA 272 9.2mm ex) and see where that takes me, maybe with an exhaust adjustable cam gear, to try to extract the most from it, if this would give me a good high RPM combo, but also being able to run with the "OEM" VVT activation and benefits for the occasional mountain drive and city cruise.

So basically, I want to maximize the potential of the engine (those 123 ftlb indicate it's a good engine underneath and bolt-on components, I think) for a bit of everything, from which I can live with not excellent under 3k drivability, as long as it screams to redline. My ultimate goal is 150whp with usability, but anything towards 155, I'm willing to kill a bit of low end for it.

So, ny question is if using the 264 in and 272 ex -with or without the adjustable cam gear- is a good idea (or not), I'm more than happy to hear your advice and/or experience, and some other possible solutions.

Please see the following for dyno results:

1. Tomei poncams graph:



2. Tomei vs TODA (yes, the TODA is the one with the weak low and mid range):



3. Details on both:



Sorry for the poor quality on the last two pics. My hard drive took a dump and I had to rescue these from some random place on my phone.

TIA for reading it all and any valuable input.

[jondee86]

Spectacular necro thread revival

I was reading this thread and happened to notice the comments about trumpets. And it made me think that it might be worth your while experimenting with other designs. There are no "guaranteed to work" off the shelf trumpet solutions, as the optimum shape and length depends on a lot of engine specific factors.

For example TODA offer AE111 trumpets in 33mm, 63mm and 88mm lengths. This would suggest that for racing purposes a shorter trumpet may be more effective, and that trying different lengths would be part of the tuning process. In my case I ran short trumpets with an integral choke (a la TOM's trumpets) and AE101 ITB's on my 16V.

Worked well for me, but your engine is completely different from mine, so you need to discover what works best for you.

Cheers... jondee86

[YoShImUrA]

Hi Jondee, thanks for chipping in. I've wondered about this, but I've been told by Sam Q (SQ Engineering), who sold me the stacks and has dyno tested them that the gains are negligible and that due to the engine's harmonics, I'm better off just putting the largest ones I can fit... I also got similar input from Ronny from Socal. If I can get someone to lend me a set, I'm happy to test the differences and back it up with a dyno.
I also tested a crazy set of stacks for comparison with the Tomeis, and I got an identical curve and figures...

[oldeskewltoy]

Hmmmm, torque and hp seem to cross closer to 6250 then 5250... 1st dyno does cross @ 5250.......





never the less.... I've forgotten, do you have flow bench results?? That might help in determining if a longer duration exhaust cam would help........