3.2 to 3.4 low on power - help me find the way

[safe]

Originally Posted by infraredcalvin

I don’t suspect a fuel delivery issue,

I wouldn't either since you have AFRs close to the right neighbourhood.

My stock euro 3.2 with ITBs and EFI have 220ish at the wheels. Your engine should be capable of 250 with larger capacity, higher compression and bigger cams.

[infraredcalvin]

Originally Posted by safe

I wouldn't either since you have AFRs close to the right neighbourhood.

My stock euro 3.2 with ITBs and EFI have 220ish at the wheels. Your engine should be capable of 250 with larger capacity, higher compression and bigger cams.

This is my fear, everything adding up except a PO miscalculation of compression. I’d hate to find out I’ve got a twin plug 3.4 with 8.5 or less compression…

[flat6pilot]

Originally Posted by infraredcalvin

I’d hate to find out I’ve got a twin plug 3.4 with 8.5 or less compression…

A turbo would quickly solve that issue.

[jpnovak]

Even low compression would not decrease power output this much.

An early S profile should give you about 78-80 crank Hp/L. Meaning - you should be seeing at least 225Hp to the wheels.

What pistons are in there? 10.5 doesn't mean much. Do they have valve pockets? ARe they CIS style pistons with a wedge dome? If there is a dome that prevents proper cam timing due to valve interference issues?

That engine should make over 200 ft pounds of torque. Peak torque should be at around 5500 rpm and yet you peak at 175 at 3k rpm.

Is there a chance of wheelspin on the dyno? The curves do not specifically show what I would call wheel spin but there are some strange steps in the outputs.

I would verify cam timing and also profile.

how much clearance do you have on the rain hats to the top of the stacks? Are they metal or plastic? Are they being sucked down from being too close? Are you limiting flow from being too close?

[infraredcalvin]

Originally Posted by jpnovak

Even low compression would not decrease power output this much.

An early S profile should give you about 78-80 crank Hp/L. Meaning - you should be seeing at least 225Hp to the wheels.

What pistons are in there? 10.5 doesn't mean much. Do they have valve pockets? ARe they CIS style pistons with a wedge dome? If there is a dome that prevents proper cam timing due to valve interference issues?

Not sure, the 10.5 came from a reference the PO made in one of his old posts here on the bird. I have a feeling he was sniffing around for similar answers, but maybe a bit proud? I pulled engine for the purpose of measuring cams and checking the mech timing. Thanks for the idea on timing due to interference, didn’t think about that, will report back.

Originally Posted by jpnovak

That engine should make over 200 ft pounds of torque. Peak torque should be at around 5500 rpm and yet you peak at 175 at 3k rpm.

Agreed! 189 tq at 3100-3200, tells me mech timing is off… why, I’m eager to find out!

Originally Posted by jpnovak

Is there a chance of wheelspin on the dyno? The curves do not specifically show what I would call wheel spin but there are some strange steps in the outputs.

There may be some wheel hop, car squats pretty good on pulls, I’ll post a link to a vid showing all three pulls.

Originally Posted by jpnovak

I would verify cam timing and also profile.

how much clearance do you have on the rain hats to the top of the stacks? Are they metal or plastic? Are they being sucked down from being too close? Are you limiting flow from being too close?

Will do, clearance is about an inch, hats are metal. Along with muffler tests I could run them open for a pull as well….

[infraredcalvin]

Dyno link:

https://youtu.be/yXccX_duoEI

[stownsen914]

Consider doing quick runs with the filters + hats removed (briefly, don't want to suck debris into the engine), and with exhaust removed. Not sure either of these if your problem, but they're really easy to do and rule out.

[stownsen914]

Originally Posted by safe

Unless one camshaft is 180 degrees off, then 1 and 4 would fire at the same time. It would fire on all cylinders and run pretty even, in theory, but what would really happen?

I believe the idea is that you don't want two cylinders on the same firing cycle, firing at the same time (edit - for example top and bottom plugs on the same cylinder). In a wasted spark arrangement (and when set up correctly), #1 and #4 will fire at the same time, but only one of them is on the power stroke. Hence one of them is "wasted". I'd guess it's to reduce load on the coil of having to produce enough spark to fire two cylinders/sparkplugs on their respective power cycle at the same time.

[safe]

Originally Posted by stownsen914

I believe the idea is that you don't want two cylinders on the same firing cycle, firing at the same time (edit - for example top and bottom plugs on the same cylinder). In a wasted spark arrangement (and when set up correctly), #1 and #4 will fire at the same time, but only one of them is on the power stroke. Hence one of them is "wasted". I'd guess it's to reduce load on the coil of having to produce enough spark to fire two cylinders/sparkplugs on their respective power cycle at the same time.

Yes, what I meant was IF ONE cam is 180 degrees out in wasted spark cylinder 1 and 4 would be on power stroke at the same time resulting in... something strange, that would run.
Some moto gp bikes used this configuration and called it "big bang" to get traction advantage. Bigger bang spaced out more.
In an set up where cylinder 1 and 4 uses the same coil, it probably wouldn't fire reliably because there would not be enough energy in one coil to fire to plugs on power stroke.

[safe]

Originally Posted by infraredcalvin

Dyno link:

https://youtu.be/yXccX_duoEI

Yes, it sounds really sluggish and strangled.

How is the throttle response?

[Tom_in_NH]

It sounds off, like its not timed correctly or not hitting on all six.
Another thing to mention: It's running twin plug with two Electromotive HPV-1's, which run in waste spark configuration.
Usually one DFU runs the upper plugs, the second DFU runs the lower plugs. When checking timing with these units, you need to check timing on both the upper and lower plugs. The early HPV DFU's are not the most reliable. Mike Bruns has stated that he has seen them drift considerably.

[infraredcalvin]

Throttle response is ok, best describing word is LAZY, once out of the torque butt dyno is telling you to shift, look down and you’re only at 4500-5000 rpm, it’s painful to wait to shift after that.. At speed it immediately makes you think it needs a lightened flywheel…

[pocv0]

I'm no expert , but I've built several Porsche race engines with Webers over the years. I think you should look at cam timing first. Next I would look at your jetting, 50 idle is too small, 150 mains are too small. On my 3.4 liter with GE80 cams I ran 65 idle, 160 mains, and 200 air correction at Willow Springs. Another important thing to look at is the enrichment ( accelerator pumps) you need to make sure its pumping, I'm not sure what the correct amount is per stroke, but make sure they're producing a steady stream of fuel when actuating the pump. Could be clogged , or the pump is not working. That's probably why you have no power out of the corners. My 3.4 ignition timing was set at 12 degrees BTDC at idle , and a total of 36 degrees at 7000 rpm. And I agree with the post above, the chokes ( or venturis) are a little large , but for a full race application it might be ok. I ran 36mm on my 3.4 liter . I was also running Electromotive twin plug, crank fired. One more thing to look at might be a ground problem on the HPV-1...... I had that happen at the track once, also had a coil pack fail as well. I hope some of this helps !

[pocv0]

One last thing- I currently have a '77 backdate with a 2.7 liter, 10.3 CR, Weber 40IDA3c's, tall manifolds, and Elgin E cams. Mains are 135, idle 60, air correction 180, emulsion tubes F3, and the engine makes 245 at the crank. idle ignition is 12 btdc, 32 degrees total. just an FYI. Your 3.4 should be up around 260-270.
one more thing--- check the compression . you should see around 155 psi if you indeed have 10.5 :1 compression.

good luck!

Howard

[mikedsilva]

Hate to say it, but in my limited experience, I went throught a similar situation. In my case, it turned out the pistons were low compression. Couple the low compression with a Mod S cam, and it ran like a dog. I pulled it down, rebuilt it with correct compression pistons, and it came alive.
While the motor is out I think you need to CC it. Until that is determined, so that you know definitively what you have (as opposed to what PO told you), everything else might not be time well spent.

[roblav]

Interesting because I'm going through something similar with jetting on a new engine I just built:
Carrera 3.0
9.5:1
Webcam Mod S cams
PMO sent 46's with 38 vents, 150 mains, and 50 idles.
Transition is bloody awful... weak.
Step 1 is try 60 idles. If not enough, then I'll go up on mains.

[infraredcalvin]

Had a couple of hours at the shop:
Took off carb assembly and measured intake ports at heads: 44mm (looks to have had some work done to them)
Checked valve adjustment : OK
Performed another leak down test: all cylinders less than 2%
Checked left hand cam timing: 5.18mm - points towards S cam
Still need to measure cam lift - gotta figure out reliable way to hold dial indicator.

[dannobee]

Bolt a piece of steel bar stock to the valve cover surface using the stud. Then put a magnetic base dial indicator on the piece of steel.

[roblav]

What's the exhaust port size?

[infraredcalvin]

Originally Posted by roblav

What's the exhaust port size?

42mm exhaust…