I'm going for it. 4 exhaust cams!! :)

[Mach10]

To hell with all of you...

I'm trying it too.


1992 (or 94) LQ1 in a Pontiac Fiero.

Just gotta rebuild the rest of the motor first

I'm hoping to have it together by mid-summer... Look for dyno/tune numbers then.

[Mach10]

Using DTD2K3 as a reference point, I've come up with some cam figures. I know DTD isn't that great of a tool, but given that I have some head flow numbers, and that when I filled in the baseline data (including stock specs) I was coming to almost EXACTLY what I was expecting to see, I figured I will use it basically as a playground for cam timing.

My baseline ran up 216hp@5500rpm, all things being equal exactly what GM says the motor should be making. The difference being that while the power curve is what I would expect, the torque-curve is WAY off (285ft-lbs at 2000rpm?!?). This has been a common occurance on DTD2K3. Never had this problem on 2k... So I removed the torque readings.

For simplicity's sake, I used seat-to-seat timing...

STOCK:
IVO 1.5
IVC 41.5
EVO 44.5
EVC 4.5
Int Duration: 223, 110 CL
Exh Duration: 229, 110 CL

Now, I plugged in the exhaust cam, preserving the centerlines for both cams. Basically being 3º wider on either end, the cam opens 3º earlier and closes 3º later.
IVO 4.5
IVC 44.5
EVO 44.5
EVC 4.5
Int Duration: 229.1, 110 CL
Exh Duration: 229.1, 110 CL

Immediately, I find a small gain across the powerband in DTD, peaking with a 3hp peak gain at 5500 for a total of 218hp.

After wiggling the cams back and forth, I settled on the following; I advanced the intake cam 4º, and I retarded the exhaust cam by 10º
IVO 8.5
IVC 40.5
EVO 34.5
EVC 14.5
Int Duration: 229.1, 106 CL
Exh Duration: 229.1, 100 CL
This gives a total overlap of 23 Which is pretty damn high.

On the graph, I'm showing a CLEAR gain right across the powerband, with a peak power of 233hp @ 6000, and 230hp useable from 5500-6500rpm.

Now, bearing in mind that this is seat-to-seat, the "real" valve overlap won't be quite as silly.

Now, what do the people who actually KNOW what they are doing think of my methodology here?

Obviously, the hardest part is going to be actually setting this timing. I'll have to work it out exactly how I'm going to do this.

Basically, I'm going to have to lay the on the timing flats, and figure out how many degrees of rotation to phase the exhaust cam properly. I figure I can work this out by hooking my dial guage up and setting the centerline from the max lift on the hole that's 180º out...


Whew... That's a long one. I can upload some DTD files if people want to check my math more closely

[Mach10]

Ok, it's official.

I plugged my numbers in with a bunch of measurements into Engine Analyzer Pro, and cross-compared my results with DTD.

I had made a critical error in my inputs to DTD, namely a wrong mmH20 entry in the head flow.

Basically, this is why the torque-curve was inverted.

With the PROPER specs laid in, I was getting a DTD graph that was close, and an EA graph that was even closer still to the stock numbers.


I will state the following in as neutral a format as possible:

The 4-exhaust cam is a NO GO.

With stock centerline (basically 3º extra duration on either side) you lose a whole whack of torque off the bottom end, as well as adding more overlap. At the top end, you lose power. It's a lose-lose situation. The power curve changes to become exceedingly peaky.

Playing with every convievable advance/retard combination, my previous estimae ot +4int-10Exh is by far the "best" of the bunch;

About 207hp @6500 rpm, with clear losses down the line. I confirmed these numbers with EA (MUCH more accurate, but also more complicated to set up and use).

What I think is happening is that Your_ID is feeling the loss of bottom end REALLY badly, and that the sharp rise when the motor comes on-cam makes it feel MUCH faster. The 3.4TDC in stock trim has a pretty flat torque-curve past about 3000rpm. Making it peaky fools the assometer into thinking that it's quicker than it really is.

Playing with cam timing, I've settled on stock cams, with a 4ºintake advance and 8º exhaust retard. This nets me a small low-end hit (no biggie in the lighter Fiero with 4.10FD) but a consistant 5-10hp increase over 5000-6500rpm.

I would invite Your_ID to step in and prove me wrong with dyno slips (or at least a 1/4 mile slip.

Otherwise, it's a bust, fellas.


BTW; these numbers are assuming proper and accurate tune. The LQ1 ECM will NOT like the additional duration, since there will be nearly no vacuum at idle. Frankly, I'm surprised it runs at all.

[Fierobsessed]

I'm still waiting to see how it dyno's. I have four exhaust cams laying around so I'm all ears, and eyes.

[your_I.D.]

Sorry folks I've been out of town. My current cam timimg is set at +5 intake and -4 exhaust. There will be a dyno slip as soon as I get back from Detroit which will be in about 2 weeks. As far as the power and driveability. The car never has run better. You can put all the numbers you want into a program. But real life results are want counts. I have 2 monte carlos to compare. A stock 95 and my 97. the 5 horse power differance from stock was barely noticeable when my car was stock. Yes I took a slight hit on the bottom end. It comes on so hard about 3500 it will eat my bro's 95 at the 100 foot mark and on thru all gears. Yes the cars have been compared with every adjustment i've made. No track slip but just a back street run next to shop. Like I said I'll produce a dyno slip as soon as i return from Detroit. Oh and don't forget the fact that all these results are with my engine having a a known bad exhaust guide. ~

[Husky]

a known bad exhaust guide. ~

I have 12 of those. And I can't wait for a dyno sheet on this, should be awesome.

[ryan.hess]

numbers roxxorz my boxxorz. Keep up the good work

[RednBlack]

This is several times I've seen guides move. Most disturbing. Some go up, some go down. We need a fix.

Although, never seen one trash yet because of it.

Interested in seeing the dyno.

[Mach10]

Sorry folks I've been out of town. My current cam timimg is set at +5 intake and -4 exhaust. There will be a dyno slip as soon as I get back from Detroit which will be in about 2 weeks. As far as the power and driveability. The car never has run better. You can put all the numbers you want into a program. But real life results are want counts.

Ab-so-freaking-lutely.

My concern is that DTD is fairly accurate to a point; At it's best, it tends to be overly optomistic, but it DOES tend to be consistant.

In addition, I was double-checking my math with EAP, which is FAR superior(but also a mofo bear to use).

If at all possible, see if they'll run you with a sniffer on that dyno. I'm eager to see what the ECM makes of it. I'm not trying to be fatalistic, just that modifying the intake duration and events has a HUGE impact on the torque-curve. My concern was that the assometer was strongly picking up the sharp hump at about 3300rpm.

One thing I HAVEN'T taken into consideration is the port math for the 96+ heads, since I was running the numbers on a 92 setup.

Entirely possible I was seeing the result of a bottle-neck at the exhaust, since modifying the intake didn't seem to affect much of anything.

Don't think I'm going to do it on my motor anyway... At least, not this iteration.

[your_I.D.]

This is several times I've seen guides move. Most disturbing. Some go up, some go down. We need a fix.

Although, never seen one trash yet because of it.

Interested in seeing the dyno.

Have you seen it on both design heads?

[Fierobsessed]

Mine was a 96, so assuming mostly everyone elses isn't... then yes, they move on all models.

[SappySE107]

The 96 heads I have here are also screwed up on the guides.

What was the min port area you used as well as the inlet area inside the plenum? What length runner did you use for intake. Did you use flow numbers with the manifolds in place?

[richlo65]

any update on the numbers?

[your_I.D.]

What was the min port area you used as well as the inlet area inside the plenum? What length runner did you use for intake. Did you use flow numbers with the manifolds in place?

? You asking Mach10 I assume.

[Mach10]

I ran the iterations based on stock 91-93 head flow math, with a standard intake that didn't change during comparison. Measurements were taken of the LIM and the plenum ports, but I wasn't able to extrapolate the runner length and plenum volume, so I discarded them in favor of a simple single-plane manifold that should negate most harmonic gains.

The conclusion I came to was that I was not taking into account harmonic tuning of the intakes, but rather going by the cam profile's ability to pull air given the lift and duration specs of the camshafts.

While it won't tell the whole story, I believe it's a valid comparison because between the two runs, the only metric that changes was cam-timing.

Now, if by some lucky coincidence the exhaust cam profile is the one that perfectly matches the intake characteristics, then a simple dyno will prove me wrong. And if the power levels stayed more-or-less constant, I'd be willing to give it a go on the basis that the baseline simulation does not take into account the intake advantage.

But in terms of moving air, it seems to hinder rather than help. ALL the iterations I've ever done with this motor show the restriction point as being the exhaust timing, very likely due to emmissions reasons. Adding a couple of degrees intake duration while not touching the exhaust does little except move the VE up the power band a little, and kill manifold vacuum until 1500rpm. Showing a 15-20% LOSS across the board tells me that there's potential for serious trouble there. I do not have enough faith in GM's intake to make the assumption that they can squeeze a full 20% worth of extra output, and then above and beyond that.

Again, PLEASE prove me wrong. I'll be the first to admit that I was wrong.