DOHC Adjustable Cam Gears

[EdKiefer]

Originally Posted by Meph

Hey UFO, I have a Toyota 1JZ-GTE in the car, 2.5L single turbo conversion.

I took my intake cam back to 0 and my exhaust +4, with my intake at +4 is felt a little limp down low, with the exhaust at +4 I could feel a a noticeable amount of grunt 1500-2000 range, it didn't seem to really help below there.

I also pulled my a/f ratio back from 15.6:1 to 15.87. My injection times crusing at 40-50 miles an hour seemed to drop around 0.1 ms (from say 1.2 to 1.1). Im going to add another degree or two of ignition take more advantage of the lower a/f too.

My trip today was 32.5 mpg, not as good as my 34.5 mpg tank last time, but it was only 40 miles of driving, on some extreme hills (drove up and past a ski resort) I really feel with cam and a/f I stand to gain a decent improvement.

as cams rotate in the order exhaust->intake advancing the exhaust would remove overlap. I hope to have better results soon!

ok, well good you notice a difference with just 4deg changes .
So lets see so far . I assume you started with Ex=0, In=0 .

you tried Ex 4+ , In 4+ and this felt sluggish down low ?

The you tried Ex 4+ , and In 0 and this seemed improvement down low , did you notice any lose in upper rpm band ?

I am afraid its going to be just trail an error to find sweet spot .

[Meph]

hum I always thought it was exhaust cam that was varried but you totally correct, all th engines are playing with intake settings. Ill try t track down the settings for a stock VVT, and copy the settings that are used for my target crusing rpm.

Thanks guys!

[EdKiefer]

Originally Posted by Meph

hum I always thought it was exhaust cam that was varried but you totally correct, all th engines are playing with intake settings. Ill try t track down the settings for a stock VVT, and copy the settings that are used for my target crusing rpm.

Thanks guys!

Most VVT vary the intake by like 25deg depending on throttle/load and rpm . Like what I posted on the honda K20/24 info .
recap, idle they run it retarded , mid rpm-high loads advanced then it backs off as rpm goes up .At part throttle- light load they advance it for EGR affect .
From my understanding its very dynamic for most manufactures .

[Meph]

I was running 0 / 0 and then +4 +4, it didnt feel bad, its really hard to tell honestly, but I felt +4 exhaust gave more grunt past 1500, but didnt feel the best below, as i changed my a/f ratio leaner it would very well be the cause. I did find today ive never driven with such low injection time at 40-50 mph, probably a combination of the two changes. I upped my ignition and hope to have even better results tomorrow.

I hope to find stock intake cam vvt settings I can imitate

[EdKiefer]

Originally Posted by Meph

I was running 0 / 0 and then +4 +4, it didnt feel bad, its really hard to tell honestly, but I felt +4 exhaust gave more grunt past 1500, but didnt feel the best below, as i changed my a/f ratio leaner it would very well be the cause. I did find today ive never driven with such low injection time at 40-50 mph, probably a combination of the two changes. I upped my ignition and hope to have even better results tomorrow.

I hope to find stock intake cam vvt settings I can imitate

right the 4+ , 4+ is not changing cam spec in relationship to each other just related to crank so that would be harder to notice IMO . Just the Ex 4+ is changing overlap so that should see change . If you did something similar on intake side should be more noticeable . Does Toyota Have a VVT version of that engine , If memory is right there 3.0 straight six did (used in turbo supra's .
You might be able to hunt down some info online or from there repair manual .

[UFO]

Mmmm, 1JZ, very nice, and very nice mileage figures. I still have the Nissan straight six from my hodrodding days, hybrid turbo and intercooler, 12.89@110. I can get 30 mpg on the highway, but I don't drive it much except for the track.

[Meph]

heres something I found relating to toyota ttv-i, on the intake cam



Now it seems as though intake advancing the intake and increasing overlap produce an improvement in MPG in low to medium cruising, the opposite as what many have been thinking. Ill look for more information to back this up

[Meph]

Heres more info relating to intake timing, an advance in intake timing would help to raise compression ratio and efficiency in lower rpm.

"Dynamic CR
At low rpm, there is little-to-no ramming of the cylinder from intake charge velocity. As the piston starts to move up the bore on the compression stroke prior to the intake closing, some of the induced air is pushed back into the intake manifold. This means the volumetric efficiency (breathing efficiency) and thus the effective displacement of the cylinder is well below 100 percent."

So maybe adding +2 intake degrees to my current +4 exhaust would help to shift the power band lower in rpm (+2,+2), raise Dynamic compression raito (advancing intake valves to close sooner) and reducing overlap (+4 exhaust - 2 intake = +2 exhaust net)

Reset my timing, and see how it drives

[EdKiefer]

Originally Posted by Meph

heres something I found relating to toyota ttv-i, on the intake cam



Now it seems as though intake advancing the intake and increasing overlap produce an improvement in MPG in low to medium cruising, the opposite as what many have been thinking. Ill look for more information to back this up

Thats basiclly same as honda , only honda has 2 cam lobs for low speeds and high loads over like 5k rpm .

They raise intake timing to increase overlap and EGR affect to help with lower temps (they probably raise ignition timing and lean out too) at part throttle low-mid loads .

The problem you will run into is this is only good at one area , it would be bad to do it across the board and why OEM don't use it unless they have VVT .
I still say slightly lower overlap like you did on exhaust is best compromise with turbo , your only really tweaking the timing, any more will hurt in other parts of powerband .

Like trying to advance intake a lot for good low rpm/part throttle would give bad idle, very rough sluggish off the line .

[EdKiefer]

Originally Posted by Meph

Heres more info relating to intake timing, an advance in intake timing would help to raise compression ratio and efficiency in lower rpm.

"Dynamic CR
At low rpm, there is little-to-no ramming of the cylinder from intake charge velocity. As the piston starts to move up the bore on the compression stroke prior to the intake closing, some of the induced air is pushed back into the intake manifold. This means the volumetric efficiency (breathing efficiency) and thus the effective displacement of the cylinder is well below 100 percent."

So maybe adding +2 intake degrees to my current +4 exhaust would help to shift the power band lower in rpm (+2,+2), raise Dynamic compression raito (advancing intake valves to close sooner) and reducing overlap (+4 exhaust - 2 intake = +2 exhaust net)

Reset my timing, and see how it drives

Sure you can try it, but its going to be hard to see change as its only 2deg shift, but maybe you can tell from adjusting ECU specs, if you know what certain specs (ignition advance, A/F ) could do before without side affects .