Why is my car a dog?

[flightlead404]

I just modded my car which was running great before I started the project. Now it's a slug and I'm trying to figure out why.

By "it's a slug" I mean it feels just like an old Chevette I had in college with a blocked catalytic converter. Incredibly low on power and I'm absolutely hitting boost. It's a slug, slower than a dump truck off the line. Difficult to express how poor the performance is.

What I did:
-Put in new SC cams, timed to 1.8mm I believe (whatever vendor recommended) (new rocker bushings, refurbed rockers)
-Sachs lightweight sport clutch package
-Flywheel lightened a little and cut for 60-2 tooth pattern
-Went to Denso COPs running in wasted spark from a microsquirt - new NKG BR8EIX plugs
-Transmission rebuild

I had previously put in FrankenCIS, RarlyL8 headers and dual outlet hooligan, K27/29, Tial F46 .8 bar, tk longneck intercooler. It was running like a scalded dog!

I have the base idle mixture set around 13.8, but I believe this only matters at idle. Pretty sure (correct me if I'm wrong) but the idle mixture is mooted above 1,500 rpm ish. Then its basically set by the CIS airflow metering arm modified by the WUR. I'm running all 100% VE on my AFR tables so its essentially identical to a stock CIS at the moment.

Car idles beautifully, rock solid, smooth, steady. Idle timing is 10 BTDC. Off idle is just super low power, but it's very smooth. No missing or anything.

I have confirmed the crank angle offset with a timing light. The timing is exactly what the computer thinks it is.

Since I haven't changed the fueling, its essentially stock CIS at this point, the only thing I can think of is the ignition timing is GROSSLY out of spec. I can't think how I could have screwed anything up on the other component swaps that would have this behavior.

I modeled the stock ignition mechanical advance and vacuum advance and retard in Excel and built a slightly more advanced than stock ignition table. I'm struggling to believe this table is that far out of whack.

Any thoughts would be appreciated.

[Tippy]

Did you put a timing light on it to confirm?

Sounds like your suspicions are correct if it runs doggy but smooth.

Or, the cam timing could by way advanced. If it pulls like a freight train up top, that could be the issue.

[Bigtoe32067]

I'd vote on cam timing being off. Seems like most anything else would give more evidence.
Stupid question but are you running cats? If they're plugged it would do that.
Are you actually building boost?
Tony

[Porsche 935]

You don't have enough timing in the lower kpa range. 65-80 kpa at 2300 should be double that.

[GJF]

+1 on not enough timing down low. you should ramp from idle to 2500rpm to atleast 36 BTDC. And as you are on boost climbing RPM's take timing away. Doing this alone will wake up the response dramatically.
Advanced cam timing will give you great low end but fall off at top end. Retarded cam timing gives you slightly less response but more RPM's on top end.

[mark houghton]

Absolutely certain that both fuel pumps are running?

[flightlead404]

I have checked the timing with a timing light, its bang on.

I have checked the fuel flow at the injectors for both consistency across the injectors at various deflections of the airflow plate as well as overall fuel delivery. Bang on. Have not independently checked the pumps. Will do that.

No cats. RarlyL8 headers and exhaust.

I'm very sure I have within a few decimal points of 1.8mm at overlap. Pulling the motor out and rechecking timing is the last thing to try lol.

I will try advancing the ignition by changing the 2800 rpm column in the table to say 34 btdc and see if things wake up. Obviously I'm loath to advance too far without knock detection.

[Porsche 935]

What kpa does your car cruise at? Under normal driving I'm at 72 kpa and have a lot more cam than you. Change 2300 to 20 degrees at 65 & 80 kpa and 36 degrees at 2800 and carry those values through the rest of the low kpa band. Should be no detonation at those kpa values, your naturally aspirated at that point.

[flightlead404]

Originally Posted by Porsche 935

What kpa does your car cruise at? Under normal driving I'm at 72 kpa and have a lot more cam than you. Change 2300 to 20 degrees at 65 & 80 kpa and 36 degrees at 2800 and carry those values through the rest of the low kpa band. Should be no detonation at those kpa values, your naturally aspirated at that point.

Its so bad right now there is no "cruise"

I'll post a new table up here when I get a chance to play with it. I must have screwed up somewhere when I tried to model the stock curve into tuner studio.

[dos531]

Do you have a wideband? What are your afrs?

[flightlead404]

Originally Posted by dos531

Do you have a wideband? What are your afrs?

I do. Idle around 13.8. I don't have other data handy but remember this isn't a full EFI install, this is FrankenCIS. So as long as all my pressures are good (they are), and I have 100% in all my VE tables, the mixture will be as delivered by a stock CIS.

[jpnovak]

Make sure your microsquirt is not set to "fixed timing" where the default is 10 deg. Make sure it says "use table" in the ignition settings.

It is common to set fixed timing when setting up trigger offset and not turning it back to correct table.

[dos531]

Originally Posted by flightlead404

I do. Idle around 13.8. I don't have other data handy but remember this isn't a full EFI install, this is FrankenCIS. So as long as all my pressures are good (they are), and I have 100% in all my VE tables, the mixture will be as delivered by a stock CIS.

So what are your afrs besides idle? You're asking for what to check, since ignition seems to be accurate. Fuel is next to verify.

[jwasbury]

have you checked stupid stuff like firing order? pretty easy to switch up a couple wires when doing a project like this. car will still run ok depending on how firing order is screwed up, but will be an absolute DOG.

yes...i did this once with my 930

[1979-930]

I don't have your system but it looks like your timing curve is slow (as mentioned) and only goes to 27*.
I have the programmable MSD with boost retard.
I have it at 14* idle and 34* by 1,800 rpm. The boost retard pulls it back to 24* by 15 PSI. I'll push it to 36* or 38* if I ever find time to get to a dyno.
The head shape and low compression likes a lot of advance early.

[bleucamaro]

You mentioned you are 100% speed density for fueling. Like other posters asked, what does the AFR look like at other RPM's. Steady state no load 2500 rpm, 3000 rpm? Steady state driving level road, and climbing a grade?

Are you running any acceleration enrichment? When you press the accelerator, does it go lean for a second? rich?

Have you just played with the timing to see if it "feels happier" with more off idle / light load? What was the result?

[flightlead404]

Originally Posted by jpnovak

Make sure your microsquirt is not set to "fixed timing" where the default is 10 deg. Make sure it says "use table" in the ignition settings.

It is common to set fixed timing when setting up trigger offset and not turning it back to correct table.

Yep its on use table and 1st deriv for prediction, noise filtering enabled.

[flightlead404]

Originally Posted by jwasbury

have you checked stupid stuff like firing order? pretty easy to switch up a couple wires when doing a project like this. car will still run ok depending on how firing order is screwed up, but will be an absolute DOG.

yes...i did this once with my 930

yep firing order is correct, wasted spark so COPs are paired, and it idles etc smoothly which it wound't do if I were missing or firing out of order.

[flightlead404]

Originally Posted by bleucamaro

You mentioned you are 100% speed density for fueling. Like other posters asked, what does the AFR look like at other RPM's. Steady state no load 2500 rpm, 3000 rpm? Steady state driving level road, and climbing a grade?

Are you running any acceleration enrichment? When you press the accelerator, does it go lean for a second? rich?

Have you just played with the timing to see if it "feels happier" with more off idle / light load? What was the result?

To date I have only driven it around the ramp and up and down a long driveway. Its too low performance to take on the road.

Yes I have lean tip-in. This is an expected behavior with CIS, where you open the throttle but the air metering plate is so far upstream. I don't have a TPS to to enrichment there.

Have not fiddled with timing yet other than idle timing.

[Tippy]

Detonation at low RPM, low loads shouldn't be an issue. Give her some timing.