DuPuis Family Cobra Build

Jim K said:
Yeah....dry chemical makes a friggin mess, and you you have to take the intake off again to clean it up.

Do you need to ask how I learned that one?
Click to expand...
I tell folks that my experience boils down to “You don’t want to try it that way. See this scar?”
 
Well, yesterday was a big day. I went through system by system and powered everything on one thing at a time.

Really, everything went pretty well. I'd forgotten to tighten a few fuel fittings and so those leaked (oops), and I had gotten the Microsquirt outputs backwards - I thought they provided +12V to power relays, but they actually ground the input. So I had to switch a couple of wires from ground to positive, and that fixed those outputs.

The video on this one will be longer and I'll probably publish it next week.

The fact that the engine tried to fire just based off of a little residual fuel and the ignition is really exciting. Obviously that doesn't mean it will run, but it tells me I can't be too far off as far as how I set up the engine, and obviously the work and details I put into making the wiring harnesses, finding a VR sensor to use for the crank position sensor, seems to have paid off. I was just going to be happy if I saw a blinking light, but that engine tried to light off instantly.

I spent some time last night going through the calibration files for the Microsquirt and making an initial baseline tune that I think should be enough to get the engine to fire. I'll poke at it some more, but it has a lot of default values that look reasonable (at least to get the engine to start) and I made some adjustments in areas that I thought were significantly off.

I would really like to start the thing this week, but I don't see that happening - I have hernia surgery on Thursday and there are still some details I need to take care of on the car before I try a real first start, more than anything to make sure that I have everything out of the way of the exhaust and moving parts. I also should pull the headers and put the header wrap on them before first start. The fact that I know that I have things to the point where it could, in theory, start is a great feeling.

The video on this one will probably be published next week.
 
Ted said:
That won’t be today. If nothing else that’s a “whole family must be present to witness” event.

Plus I’ll need extra people to hold (and probably use) fire extinguishers.
Click to expand...

Too bad I'm not around, I could hold the beer!
 
Well, I’m declaring the Cobra ready for first start now. Just need to see if there’s a break in the weather before Thursday, otherwise it’ll be a while.
 
Bill said:
Too bad I'm not around, I could hold the beer!
Click to expand...

But can you also “watch this”? Because it’s important to be able to hold my beer AND “watch this.”
 
Ted said:
But can you also “watch this”? Because it’s important to be able to hold my beer AND “watch this.”
Click to expand...
My dad worked as an electrician most of his life. He said he never made foreman (not true) because he didn’t smoke so he couldn’t stand around with a cup of coffee in one hand and a cigarette in the other.
 
  • Like
Reactions: Ted
jsstevens said:
My dad worked as an electrician most of his life. He said he never made foreman (not true) because he didn’t smoke so he couldn’t stand around with a cup of coffee in one hand and a cigarette in the other.
Click to expand...

I was more thinking “hold my beer and watch this!”
 
Ted said:
But can you also “watch this”? Because it’s important to be able to hold my beer AND “watch this.”
Click to expand...

GoPro in one hand, beer in the other? Yeah, I think I can handle that...
 
  • Like
Reactions: Ted
From what I’ve seen on TV, the way it works is: Just before you turn the key, add some suspenseful music, then cut to a commercial. When you get back, spend 5 minutes resetting the stage, then start it up and act surprised when it works.
 
Matthew said:
From what I’ve seen on TV, the way it works is: Just before you turn the key, add some suspenseful music, then cut to a commercial. When you get back, spend 5 minutes resetting the stage, then start it up and act surprised when it works.
Click to expand...

My videos are no BS, which is probably why I don’t have many subscribers.
 
denverpilot said:
Demonetized, DMCA takedown, community strike number one for the channel. LOL
Click to expand...

As I recall, you have to be over 1k subscribers to get monetization, and I'm at 634 (as of right now). The recently-released Disco video has gotten me 10 new subscribers today, which is a new record. There were some other requirements as well but they were minor ones that I already met.

I might hit 1k subscribers this year, we'll see how popular my projects are. With the Cobra wrapping up the "interesting" parts, the Disco might bring a new market.
 
Ted said:
As I recall, you have to be over 1k subscribers to get monetization, and I'm at 634 (as of right now). The recently-released Disco video has gotten me 10 new subscribers today, which is a new record. There were some other requirements as well but they were minor ones that I already met.
Click to expand...
I posted one video of my son playing a classical piano piece at a school recital to show to his grandparents.

Was taken down the next day with the Youtube DMCA notice nastygram. I promptly lost on appeal to keep it up and was given a strike.

Apparenly, Universal Music Group feels they own copyright to the full public domain body of multi-century old piano artists, because they apparently recorded and published some symphony orchestra playing the same piece.

:oops:
 
ElPaso Pilot said:
I posted one video of my son playing a classical piano piece at a school recital to show to his grandparents.

Was taken down the next day with the Youtube DMCA notice nastygram. I promptly lost on appeal to keep it up and was given a strike.

Apparenly, Universal Music Group feels they own copyright to the full public domain body of multi-century old piano artists, because they apparently recorded and published some symphony orchestra playing the same piece.

:oops:
Click to expand...
He must have played it well enough to sound like a professional recording! :yes:
 
IK04 said:
13.
Click to expand...

I've actually gotten 20 new subscribers in the past 24 hours, which is definitely a record. That's approaching the number of subscribers I normally get in a month.
 
As promised, more details on yesterday's first start:

With my surgery for tomorrow and giving myself confidence that it would in fact fire up easily after Sunday, I decided to give it a whirl since the weather cooperated.

The car started right up with its guessed calibration. It's definitely too rich, but it wasn't so rich it wouldn't run or blow black smoke. I don't have any idle air control valve (this was intentional in the design) so I found at first that the idle screw was set too low (not surprising) and turned it up. For break-in you want to be between 1500 and 3000 RPMs, so I turned it up to 2000 to start while looking things over.

The cam break-in part didn't exactly go off perfectly, which frankly wasn't a surprise. After about 6-7 minutes the lower radiator hose blew off, and I had to put it back on and refill. But I let the engine cool for a bit first since I didn't want to just pour new water into a hot engine, that's how you break things. The engine had gotten hot enough for me to check the valve lash, which was on the loose side for all of them (better than the tight side!) but not awfully so. Ideal valve lash is 0.012" and I measured 0.013-0.029", with most of them being 0.015-0.018". I now have notes so I can go back and make adjustments and try again.

I then refilled with water and ran it again (a hose blowing off is why I started off with water and not coolant). I'd been running without the valve covers bolted down so I could make sure the valvetrain was operating properly. It was, but I also found that on the driver's side where the breather is, the valve covers are just barely too close and will hit a rocker when down all the way, requiring spacers. So I ordered spacers and gaskets. There was enough oil leaking out without the valve covers bolted down that we got a little flash of flame and decided that was enough. So if you're supposed to do 20-30 minutes for breaking in a cam, we did about 10-15. I'm not sure if it screws things up to break up your cam break-in into sections over multiple days, but I think it'll be fine. And then I'll be able to get the spacers, adjust the valve lash, and try again.

Overall, though, everything seems to be working as I intended. I planned on having the valve lash on the looser side since too tight is worse than too loose, and I knew I would need to adjust it after getting proper hot numbers. Everything was a bit loose there. The timing gears I bought were the "quiet" gears and while they make some noise, it's not super loud. The alternator charges perfectly and was making 14.1V. The gauges all work perfectly. The engine sounds strong, has a strong lopey idle from what I've heard of it, and I'm sure will sound better once I get things dialed in and a proper engine calibration. There was no smoke, no blow-by, the engine makes great compression. One little puff of oil smoke when first started up out of one cylinder, which isn't unexpected. The ignition system seems to be firing perfectly and as far as I can tell the ignition advance is working, although I haven't hooked up a timing light yet to confirm that. I know that the RPM signal is going to the MegaSquirt from the EDIS, and it's being processed correctly, or else the engine wouldn't run, so I'm going to assume that the signal from the MegaSquirt to the EDIS for spark advance is also working correctly.

Initial impressions of the individual throttle body intake are that it's responsive but not uncontrollably so, which is good. Driving it on the road will be the real test of that. I also am not certain if I got all the air burped out of the system (and in fact am pretty sure I didn't). Once the engine got warmer I noticed the coolant temp indication fluctuating between 195 and 180, which makes me think the thermostat would crack open, a rush of water would come through (the electric water pump is on/off and so always running at full capacity) and then close again, but I bet there's some air in there still. Once I gain more confidence in the cooling system I'll switch it over the normal coolant and do a full and proper bleed. I didn't have the HVAC wiring done yet so I couldn't test to see if the heater was blowing hot.

I did drive it back into the garage from outside, and what a great feeling. I can't wait to drive it on the road!

A lot of effort, but the fact that it's all come together as I expected is really, really satisfying.
 
I’m glad you didn’t say it came from together. And you didn’t spray down your hot engine. (Infamous PoA thread references were required. Sorry! )
 
With all that intake and twitchy throttle, I hope you have a heavy enough flywheel. Otherwise, it gets pretty old trying to maintain RPM in cruise....
 
IK04 said:
With all that intake and twitchy throttle, I hope you have a heavy enough flywheel. Otherwise, it gets pretty old trying to maintain RPM in cruise....
Click to expand...

Nope, lightweight aluminum flywheel, lightweight balancer. The goal was to make the drivetrain as light and responsive as possible.
 
Ted said:
Nope, lightweight aluminum flywheel, lightweight balancer. The goal was to make the drivetrain as light and responsive as possible.
Click to expand...

Yeah, I figured so. Great for autocross. I suppose that big ol' crank has enough mass to make up for it.
 
IK04 said:
Yeah, I figured so. Great for autocross. I suppose that big ol' crank has enough mass to make up for it.
Click to expand...

Every project has design goals. While I wasn't trying to make this the lightest weight car possible (if I was, I would've done some things differently like gone with a 302-based engine), I've never found myself saying "I wish this car was less responsive" and was trying to make the drivetrain really lightweight and responsive, plus also very tight. As little delay as possible between moving my right foot and the engine responding. I love the super responsive nature of sport bikes, for example, and react well to them. Sure, if you're talking about a land yacht on a long highway trip it's one thing, but for a sports car like this, I think I'll enjoy it. If I want to drive a couch that day I have other vehicles that fill that role.

I did a lot of ideas with this car that have all appealed to me but that I've not had an opportunity to do elsewhere, combined. In the end we'll see what I think of it.

On first start the throttle was actually less twitchy than I expected, however I think part of that is because the thing is running too rich and with the acceleration enrichment gets way too rich.
 
Ted said:
If I want to drive a couch that day I have other vehicles that fill that role.
Click to expand...

You can borrow the Avalon. LOL.

(Yeah we bought it. Well we will once we get some title junk sorted out. People dying prior to 2017 in CO is a title headache. — After 2017 a dual named title is automatically Joint with Rights of Survival now unless requested specifically not to be. Which means changing the title instead of just showing a death certificate.)
 
I’m sitting on the couch recovering from surgery yesterday, and watching some episodes of Engine Masters where they talk about carb vs EFI. Of course they used a bolt on TBI Holley setup as opposed to having to custom make the harness and all sorts of other custom bits for the Microsquirt and Ford EDIS like I did on the Cobra.

For a long time in this process I had really wondered about whether I was making the right decision with all the extra effort and time it was taking in the build. When the engine just fired right up easily and with no problems, I think that it shows I made the right call. Of course I haven’t tuned it yet, and there are potentials for issues as I start to run higher horsepower. But EFI will pretty much always be consistent and just work, no worries about gummed up carbs or the like.
 
Ted said:
I’m sitting on the couch recovering from surgery yesterday, and watching some episodes of Engine Masters where they talk about carb vs EFI. Of course they used a bolt on TBI Holley setup as opposed to having to custom make the harness and all sorts of other custom bits for the Microsquirt and Ford EDIS like I did on the Cobra.

For a long time in this process I had really wondered about whether I was making the right decision with all the extra effort and time it was taking in the build. When the engine just fired right up easily and with no problems, I think that it shows I made the right call. Of course I haven’t tuned it yet, and there are potentials for issues as I start to run higher horsepower. But EFI will pretty much always be consistent and just work, no worries about gummed up carbs or the like.
Click to expand...

I would wait until you get the EFI all sorted out before you start the parade, lol. Not that I disagree at all with EFI being better than carb in the least. My 351w fired right up with a carb and Pertronix electronic distributor when I rebuilt it several years back. Set base timing within the first couple minutes of running and within 20 minutes I had the idle adjustment set. Haven't touched it since, although it takes 10-15 seconds of cranking to start if it's been sitting for a week or more just to get fuel up to the carb. I could solve that with an electronic fuel pump but it's not worth messing with to me. Starts within 2 seconds any time after that first cold start. However, if EFI were an easier option for the marine-application I would have certainly looked at it. My next boat (if I ever bite the bullet to upgrade) will absolutely have EFI.
 
SoonerAviator said:
I would wait until you get the EFI all sorted out before you start the parade, lol. Not that I disagree at all with EFI being better than carb in the least. My 351w fired right up with a carb and Pertronix electronic distributor when I rebuilt it several years back. Set base timing within the first couple minutes of running and within 20 minutes I had the idle adjustment set. Haven't touched it since, although it takes 10-15 seconds of cranking to start if it's been sitting for a week or more just to get fuel up to the carb. I could solve that with an electronic fuel pump but it's not worth messing with to me. Starts within 2 seconds any time after that first cold start. However, if EFI were an easier option for the marine-application I would have certainly looked at it. My next boat (if I ever bite the bullet to upgrade) will absolutely have EFI.
Click to expand...

I get what you’re saying, and the reality is that if I’d put in a carb and distributor, timed correctly, it probably would’ve started similarly the first time. When I had my boat with a standard dizzy and Quadrajet, I thought about upgrading to distributorless and EFI (or even just TBI) but it didn’t make sense for how well it started and ran.

With that said, ultimately the ease of tuning the electronic stuff and consistency of it starting regardless of how long it sits I think is a benefit. The fact it started so easily and well first time helps convince me of that.
 
I’m continuing to binge watch Engine Masters. Of course all of what they do is full power dyno runs but they’ve tested a few of the things I was doing on the Cobra.

One was the electric water pump. They run most of their engines on the dyno with electric water pumps, which in that application makes sense since it ends up being easier to hook up when you're swapping engines back and forth so regularly. They did comparisons between the same engine with electric and mechanical water pumps, and also adding in an alternator. They found the mechanical water pump only stole about 2-3 HP, and that was up around 5500 RPM. The alternator stole more horsepower, something around 4 as I recall. Of course the amount an alternator steals depends on a lot of factors, not the least of which is how much power it produces.

I didn't go with the electric water pump for horsepower savings, though, it was for my goal of wanting to minimize rotating inertia and also just seeing how well it worked. But it was interesting to see their dyno results (albeit not surprising).

Looking at some of the dyno runs they've been doing with cam specs does make me wonder if the Isky 381333 cam as opposed to the 381368 cam, which has the same lift (0.476") and still a solid flat tappet but has 290 degrees advertised duration instead of 270, and 250 degrees @ 0.050" as opposed to 228. I figured that with running 1.7:1 rockers instead of 1.6:1, plus running the lash a little on the tighter side (Isky recommendation) I can push the effective lift and duration up a bit and move the RPMs up a little too. I think it will be fine and I'm certainly not pulling the cam now, but it does make me think that once I start driving it, I'll find I want more revs out of the engine than the combination will produce with that cam.
 
The four-cam 4.6L in my Marauder has a clutch on the alternator that disconnects the drive above a certain RPM or when the throttle is WFO. less inertia and spinning mass during the .5 second upshifts.

I have a Meziere electric pump, but it still has a pulley on it that spins freely, so there is a little loss there...

That cam sounds pretty sporty, but since you have an intake system that can suck huge CFM, you might be right. Again, driveability will be what you want it to be and if a screaming top end is paramount, then plan for the nasty cam and accept the soggy low end...
 
You must log in or register to reply here.
Back
Top