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Just following up on this terrific thread - I've got a few questions!

First, from Al, what is your idle rpm? I have GSC S1s and a ported head and at around 950rpm, am seeing ~12inHg. These are with my cam gears set to zero. I'm assuming here that idle vacumn drawn correlates with idle rpm, but am happy to be corrected on that. If it does - is my idle vacumn acceptable for this rpm, or would there be gains to be had by retarding the ex cam/advancing the inlet?

My second question was (to Alpha/Al/Eden), given that ignition timing advance is linked to the inlet cam - did you advance the ignition timing across the board by 2deg for each 1 degree of inlet cam retard to compensate, or did you leave timing untouched?

Thanks for your input :)
Adjusting the cams as such allowed me to run the bone stock idle setup, with no adjustments. It can vary a little, but during the cold months it was 750-800. With HKS 264's and no cam adjustment it was more like 600-700.

No timing adjustments since I am on stock ECU. ;)

Al
 

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LOL, fair enough on the timing then Al :) I'd dearly love to idle lower, but with the cams/fuelling/timing as they stand presently, I think the rattle from my RPS C-C clutch would start to irritate me.

Having said that maybe I need to try it - I'm going to be adjusting the cam gears next week, starting at -2 on the ex cam and then proceeding, so once I've got it adjusted for the best compromise between idle vacuum and roughness and "snappiness", I'll give it a go!

BTW, forgot to say I 100% agree with you on the idle emissions from GSCs compared to my HKS 264s - night and day different. Out of interest, did you find these improved with cam gear adjustment?
 

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You are going to want to advance the exh cam and retard the intake cam. Start with +2 exh, then try -2 intake, that will get you most of the way there. Mine is +5,-2, and Tayousei's +5,-4 works well also.

Idle emissions did not improve much with degree'ing the cams, still reeks really bad!

Al
 

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You are going to want to advance the exh cam and retard the intake cam. Start with +2 exh, then try -2 intake, that will get you most of the way there. Mine is +5,-2, and Tayousei's +5,-4 works well also.

Idle emissions did not improve much with degree'ing the cams, still reeks really bad!

Al
Of course, my bad for writing e-mails at work ... I meant to say ex cam advance and inlet cam retard. Thanks for the advice, I'll start with those settings and see how I go :)

Bugger about those emissions :( Ah well, the pursuit of streetable, daily driveable power is all about compromise, as I'm learning.
 

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Well, I recently got back from having the cam gears adjusted. I'm pleased to say that the recommendation of 2deg advance on the exhaust cam was spot on - that was the sweet spot for idle vacuum, low rpm torque and peak power. Any further advance resulted in fantastic idle vacuum but very clearly choked my setup in terms of midrange and peak power.

The inlet cam was more interesting :) Somewhat contrary to suggestion, retarding the inlet cam - even with extra ignition timing added in to compensate - upto 4 degrees resulted in greater idle vacuum but clearly choked the motor, with compromised spool, midrange and peak power and torque.

When we tried zeroing the ex cam to see what happened, idle vacuum suffered and the torque curve was very clearly shifted to the right. I made more peak power and carried it through to 8000rpm, but sacrificed significant spool and low/mid-range rpm torque. Not a desirable outcome for a daily driven street car.

On a whim, I thought I'd try *advancing* the inlet cam. This yielded phenomenal results. Overall, with the ex cam advanced 2 deg, and the inlet cam advanced 4deg, I made peak boost 600rpm earlier; picked up upto 45lb-feet of torque where it matters (both down low and at peak) and more torque everywhere; and 40rwhp more peak power in addition to more power everywhere compared to cam gears zerod :D The tradeoff in idle vacuum was minimal.

All runs were conducted at the same boost - my street setting, 24psi.

The on-road difference is fabulous - really noticeable, much more than the numerical difference would suggest.

I don't know if this reflects the dynamics of my particular setup (3.3L stroker, +1mm valves and aggressive head porting, stock IM, medium twins, 93AKI fuel + WMI) but there you have it. A very worthwhile exercise overall, and illustrates the heterogeneity of ideal settings for individual setups :)
 

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...fantastic...phenomenal...45lb-feet of torque where it matters (both down low and at peak) and more torque everywhere; and 40rwhp more peak power in addition to more power everywhere...on-road difference is fabulous...very worthwhile exercise overall...
So I assume you liked the results ;) I'm going to try messing with this, too.
 

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Discussion Starter · #49 ·
Shombre those are very interesting results. Ill see if Al sees a similar gain and if so, then Im gonna change it on a dyno to see what gains are to be had. I wouldnt mind faster spool and 40-50 tq and rwhp for almost nothing :) thanks for sharing those results!
 

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It will be a while before I do anything with cam adjustments, working on the car right now.

IIRC, I did advance the intake cam when I first advanced the exhaust cam a while back, with no good results. Every car is different for sure.

Al
 

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Hi guys, thank you for the kind words!

I have to say first of all that these were the most unexpected gains I've had before. Not *one* of my previous motor/cam/turbo setups (previously unloved 1JZ/HKS 264s/twin 2560s, pristine 2JZ/HKS 264s/same as my current setup) have yielded any quantifiable benefit from cam tuning. At the end of the day, the dynamics of each person's setup are clearly different enough that on fresh motors with aggressive cams, this may be a worthwhile exercise :)

I also want to put things in perspective here; I'm not running hyper-effcient turbines, 6L of displacement, QSVs, E85, VVTi, or 10:1 SCR (9:1 in fact), so it's not like I have "insta-boost" from 5% throttle or whatever. But it is, no question, a *much* more fun car to drive on the street now, in its controlled, sustained savagery of power delivery ;)

Nick - ROTFL, when you put it like THAT, yeah, it was an agreeable experience ;)

Eden - go for it, I'd love to see free (relatively speaking!) gains on your setup :) You and I share a street focus, so I think you'll find it fun. Please post up your final settings once they're done - this may be a nice database to have for GSC S1 users. I think you may find, as Al did, that your current inlet cam settings are the best.
 

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Although mine are S2's after the talking with Greg and having the it degree'd according to the card this is what the results looked like on the cam gears.
i still need to degree my cams, while idling im only getting about 10 inHG. and when the car is fully warmed up, it stalls.

Rocketman can you post another picture? i cant see the mark on your intake cam gear. also it looks like you retarted the exhaust cam. thats the opposite of what everyone else here has done.
 

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no im using AEM V1 thats tuned for my old setup. i know i need to get it tuned as well. but it should still run the engine.

but im asking about the exhaust being retarded in that pic while everyone else is advancing it
 

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no im using AEM V1 thats tuned for my old setup. i know i need to get it tuned as well. but it should still run the engine.
With only 10hg of vacuum, the idle will need turned up to provide enough air to keep the engine running, or increase the vacuum with the cam settings instead.

Al
 

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I first off want to say this is a great thread with a ton of good info!!
Saying that today I decided to mess with my gears since they have always been just at 0. My car was idling with about 10in of vacuum at best. So I started with the ex and advanced it 3 deg and it brought the vac to about 14in of vac. I thought sweet ill mess with the intake. I retarded it 2 deg and it would barley idle, had 9in of vac and cammed like a sob, also rev'd up very slow and was not right. So I decided to try advancing it 2 deg and that brought it to 15in of vac and the car feels very responsive.
Im putting it back on the dyno and will fine tune it I just wanted to play with it first so I would have less time on the dyno. I wondered what anybodys take was as it seemed like myself and one other had to advance our intake side as oppose to retard it like most everybody else?
 

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Smaay, that ex cam is advanced. I'm not sure why the gears are labelled like that in the pic, but as we established in this thread, http://www.supraforums.com/forum/showthread.php?693663-Retard-and-advance-timing-question that direction is definitely advanced.
now you read it wrong smaay, the ex cam in picture on this page the "Rocketman1000R picture" of the hks gears is retarded not advance, i think its tricky for some ppl to read different cam gear labels right cuz if the adv/retd marks are on the inner section of the gear or outer section,
 

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Discussion Starter · #60 · (Edited)
Keep in mind that after adjusting the intake cam you have to reset your ignition timing.

Al
Apparently you dont have to. A while back i read that for us 2jz guys, the crank sensor is responsible for timing and the inlet cam sensor is just referenced for where you are in the cycle. Maybe someone can confirm that before people go out and mess with their timing tables.
 
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