Need some professional advice on cams

[Trevor]

Originally Posted by dynomatt

Harvey are you using Engine Analyser Pro? If so, I'd be keen to get some of the engine detail that I'm missing from so that I can play too.

Lobe centres for this motor would probably be about 105-110 degrees.

Trevor...I'd like more info to backup why the 10mm lift I'm proposing "is not feasible on several grounds". I'm proposing 10mm as a good start given the valve sizes, and am well aware that the valve springs are a problem. I'm proposing a change to them and also may need to grind down the bucket retainers to clear the cam. But otherwise, I'm not sure why it's a problem?

I'm exploring whether I can get the compression ratio to about 12:1 too as I think that's where I want to aim for rally use.

Matt

Hi Matt,

You have in fact detailed some of the problems you must overcome. I do not believe the modifications are feasible. I welcome you to prove me wrong and in fact would applaud you if you can do so. Sincerely I wish you the very best in your endeavor and hope you are successful.

Cheers, Trevor.

[TomsSVX]

Well, looks like you will need another test dummy. looks like the silver popped a HG recently and I am going to do it right with a different kind of build. Anyone who knows why I would want to raise lift to 8mm and reduce overlap will know what I want to do. Anyway thank you all for your input and advice, I am sure some more modders in the future will find this info very usefull.

Tom

[Trevor]

Originally Posted by TomsSVX

Well, looks like you will need another test dummy. looks like the silver popped a HG recently and I am going to do it right with a different kind of build. Anyone who knows why I would want to raise lift to 8mm and reduce overlap will know what I want to do. Anyway thank you all for your input and advice, I am sure some more modders in the future will find this info very usefull.

Tom

I guess you not mean, "to raise lift to 8mm and INCREASE overlap".

I understand there are others who have the same cam grind as you used and therefore may be seriously affected, as Harvey's intended position for the lobe centers has never been confirmed. Furthermore without this information, it is imposslble to establish any conclusions as a result of the work you have done, which as you say, could assist others in the furure and this is a shame.

Do you have any information in this regard, as nothing appears to be forthcomig from Harvey? In particular were your cams set as per OEM timing marks, or offset one gear tooth and if so in which direction?

[NeedForSpeed]

I'm guessing he meant what he said, decrease overlap. Tom has a couple turbos looking for some air to move.

Originally Posted by Trevor

I guess you not mean, "to raise lift to 8mm and INCREASE overlap".

I understand there are others who have the same cam grind as you used and therefore may be seriously affected, as Harvey's intended position for the lobe centers has never been confirmed. Furthermore without this information, it is imposslble to establish any conclusions as a result of the work you have done, which as you say, could assist others in the furure and this is a shame.

Do you have any information in this regard, as nothing appears to be forthcomig from Harvey? In particular were your cams set as per OEM timing marks, or offset one gear tooth and if so in which direction?

[svxsubaru1]

Originally Posted by oab_au

Tom you would be wasting your time using that cam in your 6 speed car. You really need to be looking around the Stage 2 that I suggested. Around 15 to 20* extra duration and more lift.

These cams that Mychailo found look the goods.
http://www.subaru-svx.net/forum/show...32&postcount=5
8.75 mm lift on each, and around 200* duration. These are very close to the set that my Son used in his 3 Lt Datsun. Running these cams, with a 119* inlet LC, 114* exhaust LC, on a model, gave these figures.

RPM 3000 4000 5000 6000 7000
Kw 73 129 182 203 204
Nm 232 309 348 324 279

These would suit the 6 speed gear box that you have, and produce the level of performance you are looking for.

Harvey.

Sorry for coming in late, but has any one tried using this cam on there SVX yet? Ive been acking for some more power up top and will staring having some some funds to get stuff done, and it seems like some cams a ecutune stage 2 would help alot. Has that much lift been used succsefully with the stock SVX vavle springs? Or do you think it would work? Would it still pass emmisions?

[oab_au]

Originally Posted by svxsubaru1

Sorry for coming in late, but has any one tried using this cam on there SVX yet? Ive been acking for some more power up top and will staring having some some funds to get stuff done, and it seems like some cams a ecutune stage 2 would help alot. Has that much lift been used succsefully with the stock SVX vavle springs? Or do you think it would work? Would it still pass emmisions?

Haven't been used on a SVX, that I know of. Used the same in a Datsun with a RB30 block with a RG25 head on it. This is the G-Tec scan of the old 240*,7.8mm lift, and the new 257* 8.75mm lift cams.

You can compair the differences that the increase in lift and duration gave, in this case. The engines are very close in specs. though the out put figures that I posted for the EG33 would be the likely results.

From what we know now 9mm is possible, so the lift will be ok. Depending what rpms you go to, stronger springs would help. Emissions should not be affected.

Harvey.

[Trevor]

Harvey,

Copied below is the collected figures/information, associated with the above extensive, impressive but disorganized post.

"8.75 mm lift on each, and around 200* duration. These are very close to the set that my Son used in his 3 Lt Datsun. Running these cams, with a 119* inlet LC, 114* exhaust LC, on a model, gave these figures."

RPM 3000 4000 5000 6000 7000
Kw 73 129 182 203 204
Nm 232 309 348 324 279

(Edit. N.B. 119* LC = 238* duration, 114* LC = 228* duration? Are these figures @ 0.050" ?)

These cams that Mychailo found look the goods
"S14 KA24DE motor (late model 240SX)
intake profile: 0.350" lift, 206 deg @ 0.050" (a bit too much duration)
exhaust profile: 0.350" lift, 200 deg @ 0.050" (almost too much duration, but probably ok)."

(Edit. The LC is not specified. "Too much duration"?? Not so eh Mychaillo!!)

"Haven't been used on a SVX, that I know of. Used the same (Edit. Presume same lift?) in a Datsun with a RB30 block with a RG25 head on it. This is the G-Tec scan of the old 240*,7.8mm lift, and the new 257* 8.75mm lift cams."

(Edit. Are these figures @ 0.050" ? The LC is not specified.)

We are advised that the information relates to a "Datsun with a RB30 block with a RG25 head on it". Specifications would be very helpful, as we are not Datsun enthusiasts. Given that one sees them as relevant.

The information one can glean, is that there was a meagre improvement registered, amounting to 8% in H.P. and 4% in torque (Torque at increased RPM). Power fell off badly at 5,650 RPM. In my book not worthy of the effort. Those involved here will be looking for much more and certainly power from 6.000 RPM on through 7,000 RPM.

The one specific which can be gained from the post, is that you place a great deal of emphasis on valve lift. You state, " From what we know now 9mm is possible, so the lift will be ok." I state that attempting an increase of 29% above the original specifications would foolhardy, all positive/negative factors taken to account. Eight m.m. is a reasonable figure, i.e. 14%. What is ultimately possible is not necessarily desirable or effective.

Advice as to your reasoning that 9 m.m. is OK, Most of all, supporting figures covering the actual gain in increased port area relative to time, that would be achieved, will I hope be provided. These figures will impress much more than irrelevant charts.

Cheers, Trevor *<)

[oab_au]

Moving the Lobe Center.

The Lobe Center (LC) or the Maximum Open Position (MOP) is the crankshaft position
in degrees, when the valve is fully open. As the valve is only fully open for a short time,
we need to arrange things, to allow the maximum amount of air to enter the cylinder. This
will only happen, if the inlet valve is fully open, when the air is flowing at its maximum
speed.

The air speed is caused by the piston speed, which reaches its maximum speed at about
84* After Top Dead Center. So if the piston moves slowly the air will follow it at the
same speed. As the piston speed increases to about 3000 rpm, the air which has to flow
through the inlet passages, tends to lag behind the piston, so that the maximum air speed
is occurring later in the cycle. Instead of it being at 84* ATDC it is occurring at about
100* ATDC.

If we want to build an engine that will have maximum torque at 5000 rpm, we need to set
the cam up so that the maximum air speed and the MOP coincide at the same time. In our
SVX .engine this is around the maximum torque peak of 4800 rpm. The air will reach its
maximum at about 114* ATDC, so we time the cam so that it is fully open at 114*
ATDC. If we want to move the torque peak further up the rpm range, we need to retard
the cam position, to have the MOP latter in the cycle, to where the maximum air speed is.

We can also use this feature to adjust the torque peak to a slightly different position, as I
did with the cam that Chike had made. As this was for the drags, I decided to retard the
cam to 121*ATDC, to stretch the torque further up the rev range, so that the torque held
up for longer up the range, and the high rev end was enhanced.

Going back to the scans of the cam used in the Datsun, we have this one where the Lobe
center is around 100*ATDC. the thing to note is the dotted curve that is the torque curve
peaks about 4500 rpm then drops off.



This next one shows the same cam retarded to 120* ATDC, you can see the way the
torque curve still peaks at around 4500 rpm, but instead of dropping off, it continues to
hold good torque to around 5600 rpm.



We do pay a penalty by a lower peak torque, but
the wider spread of torque offsets the loss, while increasing the HP, for the conditions that the quarter mile
demands.

Harvey.

[shotgunslade]

Harvey:

Thanks for this informative post. I now understand why the recommendation for the '93 Nissan 300zx camshaft for SVX's running a 3.9 final ratio 5MT was 118 ATDC. If that spec was given to the cam grinder, I suppose he would adjust the rotational location of the cam in the grinding apparatus, keyed to the indicator on the camshaft drive gear, so that, when properly installed, on the right sprockets, the camshaft would be a maximum lift at 118 ATDC. So the variables are, did the camshaft grinder grind it to specifications, and was it installed on the right gear tooth location?

Dan

[oab_au]

Originally Posted by shotgunslade

Harvey:

Thanks for this informative post. I now understand why the recommendation for the '93 Nissan 300zx camshaft for SVX's running a 3.9 final ratio 5MT was 118 ATDC. If that spec was given to the cam grinder, I suppose he would adjust the rotational location of the cam in the grinding apparatus, keyed to the indicator on the camshaft drive gear, so that, when properly installed, on the right sprockets, the camshaft would be a maximum lift at 118 ATDC. So the variables are, did the camshaft grinder grind it to specifications, and was it installed on the right gear tooth location?

Dan

Thanks Dan, as far as I know the profile was the KA24DE engine from the 240SX? the actual retard was 121* ATDC, and yes the retard was ground into the cam lobe, so that you only had to install it, without having to change anything. I don't doubt that Delta did the grind right, but it has not been checked by anyone.

How would you describe the effects of the cam change, compared to the original. Chike, Tom and Myxalplyx might like to give there impressions also,as to how it worked out in practice.

Harvey.

[shotgunslade]

It is really hard to say, because so many other things were changed at the same time, 5MT, and adjustable fpr being two of them. I am very pleased with the acceleration of the car. I have a GTech run that young Tom did before the mods, but I haven't yet had an opportunity to get a post mod run. I'm going for a track day (road track, not drag strip) this weekend. maybe I'll try to get a GTech run while I'm there.

[oab_au]

Originally Posted by shotgunslade

It is really hard to say, because so many other things were changed at the same time, 5MT, and adjustable fpr being two of them. I am very pleased with the acceleration of the car. I have a GTech run that young Tom did before the mods, but I haven't yet had an opportunity to get a post mod run. I'm going for a track day (road track, not drag strip) this weekend. maybe I'll try to get a GTech run while I'm there.

Yes I can understand, with the other changes too. It will be interesting to see how the torque curve suits the 6 speed on a circuit. I would guess that it will cover the rev range that you would use, to make it very forgiving. You know " wrong gear, wrong speed, wrong line" the torque covers it.

Like to know what rev range you used, like 4 to 6.5, 5 up?, what was your main rpm centred on.? I would like to do this next set of cams to suit the 6 speed, operating in the 5 to 7.5 range.

All the best next week end.
Harvey.

[shotgunslade]

Harvey:

I have the 2004 WRX 5 speed. Here is a table of the gears, rpms, and theoretical speed in mph:

Final Drive Ratio--3.9---------------------Wheel Diameter--24.72

Gear---Ratio----2000----3000----4000----5000----6000----7000
1------3.454-----11-------16------22------27-------33------38
2------1.947-----19-------29------39------48-------58------68
3------1.366-----28-------41------55------69-------83------97
4------0.972-----39-------58------78------97------116-----136
5------0.738-----51-------77-----102-----128------153-----179

The engine really comes on strong at 3500-4000 rpm and really digs in until at least 6500. It likes to rev. Can't really say if it is worthwhile to take it up to the 7200 red-line, especially since I'm not drag racing. Mostly I find myself in 3rd and 4th. It takes a pretty tight hair-pin to put me down into 2nd. I haven't yet found a long enough straight to get into 5th.

[oab_au]

Originally Posted by shotgunslade

Harvey:

I have the 2004 WRX 5 speed. Here is a table of the gears, rpms, and theoretical speed in mph:

Final Drive Ratio--3.9---------------------Wheel Diameter--24.72

Gear---Ratio----2000----3000----4000----5000----6000----7000
1------3.454-----11-------16------22------27-------33------38
2------1.947-----19-------29------39------48-------58------68
3------1.366-----28-------41------55------69-------83------97
4------0.972-----39-------58------78------97------116-----136
5------0.738-----51-------77-----102-----128------153-----179

The engine really comes on strong at 3500-4000 rpm and really digs in until at least 6500. It likes to rev. Can't really say if it is worthwhile to take it up to the 7200 red-line, especially since I'm not drag racing. Mostly I find myself in 3rd and 4th. It takes a pretty tight hair-pin to put me down into 2nd. I haven't yet found a long enough straight to get into 5th.

Using your info into the gear calculator here:

http://www.geocities.com/z_design_st...nsmission.html

Shows that you will do most of the work, between 4500 and 6500. the only difference will be 1st to 2nd, 6500 in 1st will drop to 3500 in 2nd. So it may be worth going a bit higher in 1st to keep it up the rev range in 2nd.

Looks good.

Harvey.

[cdigerlando]

I will be looking at doing cams for my engine rebuild and was wondering if there are any suggestions for modifications with a boosted engine (15-20 psi) running 8.5:1 compression. Great thread by the way.

Thanks

Chuck D.