I am getting ready to pick up my Cobra engine after having it freshened and awoken from being stored. Looking for some valvetrain specs here at home, I stumbled across something I wrote when I had the engine on an engine dyno. This was years ago - long enough for me to have forgotten all of the dramas we went through.
Jeez, I was thinking of running it up again on the dyno again soon (at the same place, now named Cragsted Race Engines ), but now I'm not so sure.....
A few good reasons why it pays to have some spares before you take your motor to an engine dyno...
The time had come to run the engine on Cragar Performance's Superflow 901 engine dyno. I preferred the idea of an engine dyno, because I could just imagine the number of extra things that could go wrong with the drivetrain on an entirely new car - trans leaks, convertor problems, axles seals, uni joints etc, etc. I'm a pessimist, and I could just see myself breaking all of these things before we got a decent dyno readout. In any case, I still think that an engine dyno gives more repeatable results without the chance of tyres spinning on the rollers.
I took my ENTIRE fuel system down to Cragar - lift pump, swirl pot, 2 Bosch Motorsport pumps, filter, solid supply and return lines, regulator - EVERYTHING! I wanted to ensure that I had enough fuel supply before I put everything back into the car. We used my exhaust headers, again to duplicate the way that things would be in the car. Used my Motec M800, MSD Digi 6 and MSD HVC coil, and my custom ignition leads (sourced locally).
First problem was the fact that the Motec wouldn't do an injector test. After lots of checking by both Craig Hasted and Steve from CPWS - Custom Performance Wiring Services , it was determined that the MSD wouldn't trigger without a signal from the Motec, and the Motec couldn't get a signal from the crank trigger without the engine running. Catch 22!!! With that sorted out, let's get the engine running. It fired right up, but then we found the next problem...
No Lambda signal to the Motec! Given that we were planning on running up to 20psi boost, I think it's fair enough that we use the Lambda capability of the Motec. Check the wiring again - it's fine. Check the sensor - it's fine. Plug in a Motec PLM to verify that the sensor's working - it's fine. Ring Motec, they say that everything should be OK, just check the wiring. We all know that it's not the wiring or the sensor, but what the hell - let's check it all again. Still no joy, so Craig decides to tune the off-boost settings, and get the idle running smoothly. Everyone's tearing their hair out about this damn Lambda problem. We rang Motec again, and again they say "check this, check that". At the end of the day, on our third call to Motec, they realise that we have the version of software that had a bug that didn't allow Lambda tuning like it should have!!!!!!! That's a day's dyno time down the toilet... They say they'll email the latest version of software to overcome this problem. That's good, but the newest version requires a CAN cable connection to upload the software into the Motec, not the RS232 cable that I have in my wiring loom. Now we had to courier up a CAN connection. This didn't arrive until late in the morning - there's another half a day dyno time down the toilet!!!
OK - now we're ready to make some big power numbers! The low rpm tuning looks good, the motor sounds healthy. Time for some BOOST!!! First pull to 3000rpm, not even at full load, and the motor drops a cylinder. Craig had heard/felt/detected it long before I could hear or see a problem. Lots of experience, I suppose. He said straight away that he didn't think the motor was hurt, probably just a plug lead. He walked straight in, and picked the lead first time. It wasn't a smoking, smouldering mess, but you could see where the garbage quality plug boot had melted. Funny that, I thought I paid for the best quality plug leads... Long story short, but the exhaust pipes run too close to the plug boots. Without having the luxury of heaps of time to have some new pipes made up, we just kept on tuning, and replacing the boots and leads as they eventually melted. When they melted, they would allow the spark to short out against the exhaust, creating a wave of sparks that would shoot across from one pipe to the next. Absolutely not the best way to tune a motor and a waste of 28 plug leads, but it certainly made for a spectacular light show! We also struggled with a misfire problem that eventually proved to be the MSD HVC coil shorting against the dyno stand. The Motec was also on this stand, but it didn't show any error signals.
Ready for the next drama? Blower belts... Many guys that use cog pulleys are using Gates 8mm HTD belts. These apparently work fine up to a pulley speed of around 15,000rpm. My blower pulley is spinning faster than this, and combined with the fact that I'm trying to use a thin 30mm wide belt, this was creating problems. The belt itself wouldn't snap, but it was stripping all the teeth off the belt... I took some spares with me just in case, and lucky I did. We stripped three within three full power pulls. I tried putting some preload on my blower brace to see if that would help, but it obviously didn't! I have now found out that the belt that I should be using is a Gates Powergrip belt - same pitch and width, but 30% stronger.
The end result was that we couldn't rev the motor over 6000rpm without stripping a blower belt. At 6000, the motor is making 15psi boost, 805hp and 705lb/ft torque (604kw, 950nm). This is with a super-conservative 18 degrees total timing and 11.8:1 air fuel ratio. On one run, the engine held it's torque peak to 6,400, which made 859hp @ 6400rpm. The intercooler is fantastic. The air temp out of the blower reached 163 degrees C. Into the motor was always a couple of degrees either side of 50 degrees C. Big difference!!! We tried upping the timing by two degrees at 5000rpm, and the motor made 60lb/ft more torque, so we know we have some more power up our sleeve. It's not a dyno competition contender, but I know I can put some good fuel in and have some fun if I want to!
I'm really happy with the way Craig approached the dyno session. I wanted to see big numbers from the very beginning, but he sensibly crept up on the tuning side of things. Instead of taking home a pile of detonated, melted metal in a box, I took home a motor that's making over 800hp at only 6000rpm with a super-safe tune-up. It should last me a long time, and in something the weight of a Cobra, will certainly keep me entertained for a while! None of the engine dramas were caused by Craig, and I really thank him for having the patience to persevere through my troubles.
It's still up on the air, Ash. If I could graft a decent front end onto the Cobra, I'd be keen to put it all back together. If that starts to look too expensive, I'd probably give the big block a rest and put the blown motor in the XY for a while.
Cobra Make, Engine: Venom, BF XR8 260kw, 6 speed auto
Posts: 158
Not Ranked
Inspiring! What block are you running? 950Nm is WILD!
Quote:
Originally Posted by 750hp
I am getting ready to pick up my Cobra engine after having it freshened and awoken from being stored. Looking for some valvetrain specs here at home, I stumbled across something I wrote when I had the engine on an engine dyno. This was years ago - long enough for me to have forgotten all of the dramas we went through.
Jeez, I was thinking of running it up again on the dyno again soon (at the same place, now named Cragsted Race Engines ), but now I'm not so sure.....
A few good reasons why it pays to have some spares before you take your motor to an engine dyno...
The time had come to run the engine on Cragar Performance's Superflow 901 engine dyno. I preferred the idea of an engine dyno, because I could just imagine the number of extra things that could go wrong with the drivetrain on an entirely new car - trans leaks, convertor problems, axles seals, uni joints etc, etc. I'm a pessimist, and I could just see myself breaking all of these things before we got a decent dyno readout. In any case, I still think that an engine dyno gives more repeatable results without the chance of tyres spinning on the rollers.
I took my ENTIRE fuel system down to Cragar - lift pump, swirl pot, 2 Bosch Motorsport pumps, filter, solid supply and return lines, regulator - EVERYTHING! I wanted to ensure that I had enough fuel supply before I put everything back into the car. We used my exhaust headers, again to duplicate the way that things would be in the car. Used my Motec M800, MSD Digi 6 and MSD HVC coil, and my custom ignition leads (sourced locally).
First problem was the fact that the Motec wouldn't do an injector test. After lots of checking by both Craig Hasted and Steve from CPWS - Custom Performance Wiring Services , it was determined that the MSD wouldn't trigger without a signal from the Motec, and the Motec couldn't get a signal from the crank trigger without the engine running. Catch 22!!! With that sorted out, let's get the engine running. It fired right up, but then we found the next problem...
No Lambda signal to the Motec! Given that we were planning on running up to 20psi boost, I think it's fair enough that we use the Lambda capability of the Motec. Check the wiring again - it's fine. Check the sensor - it's fine. Plug in a Motec PLM to verify that the sensor's working - it's fine. Ring Motec, they say that everything should be OK, just check the wiring. We all know that it's not the wiring or the sensor, but what the hell - let's check it all again. Still no joy, so Craig decides to tune the off-boost settings, and get the idle running smoothly. Everyone's tearing their hair out about this damn Lambda problem. We rang Motec again, and again they say "check this, check that". At the end of the day, on our third call to Motec, they realise that we have the version of software that had a bug that didn't allow Lambda tuning like it should have!!!!!!! That's a day's dyno time down the toilet... They say they'll email the latest version of software to overcome this problem. That's good, but the newest version requires a CAN cable connection to upload the software into the Motec, not the RS232 cable that I have in my wiring loom. Now we had to courier up a CAN connection. This didn't arrive until late in the morning - there's another half a day dyno time down the toilet!!!
OK - now we're ready to make some big power numbers! The low rpm tuning looks good, the motor sounds healthy. Time for some BOOST!!! First pull to 3000rpm, not even at full load, and the motor drops a cylinder. Craig had heard/felt/detected it long before I could hear or see a problem. Lots of experience, I suppose. He said straight away that he didn't think the motor was hurt, probably just a plug lead. He walked straight in, and picked the lead first time. It wasn't a smoking, smouldering mess, but you could see where the garbage quality plug boot had melted. Funny that, I thought I paid for the best quality plug leads... Long story short, but the exhaust pipes run too close to the plug boots. Without having the luxury of heaps of time to have some new pipes made up, we just kept on tuning, and replacing the boots and leads as they eventually melted. When they melted, they would allow the spark to short out against the exhaust, creating a wave of sparks that would shoot across from one pipe to the next. Absolutely not the best way to tune a motor and a waste of 28 plug leads, but it certainly made for a spectacular light show! We also struggled with a misfire problem that eventually proved to be the MSD HVC coil shorting against the dyno stand. The Motec was also on this stand, but it didn't show any error signals.
Ready for the next drama? Blower belts... Many guys that use cog pulleys are using Gates 8mm HTD belts. These apparently work fine up to a pulley speed of around 15,000rpm. My blower pulley is spinning faster than this, and combined with the fact that I'm trying to use a thin 30mm wide belt, this was creating problems. The belt itself wouldn't snap, but it was stripping all the teeth off the belt... I took some spares with me just in case, and lucky I did. We stripped three within three full power pulls. I tried putting some preload on my blower brace to see if that would help, but it obviously didn't! I have now found out that the belt that I should be using is a Gates Powergrip belt - same pitch and width, but 30% stronger.
The end result was that we couldn't rev the motor over 6000rpm without stripping a blower belt. At 6000, the motor is making 15psi boost, 805hp and 705lb/ft torque (604kw, 950nm). This is with a super-conservative 18 degrees total timing and 11.8:1 air fuel ratio. On one run, the engine held it's torque peak to 6,400, which made 859hp @ 6400rpm. The intercooler is fantastic. The air temp out of the blower reached 163 degrees C. Into the motor was always a couple of degrees either side of 50 degrees C. Big difference!!! We tried upping the timing by two degrees at 5000rpm, and the motor made 60lb/ft more torque, so we know we have some more power up our sleeve. It's not a dyno competition contender, but I know I can put some good fuel in and have some fun if I want to!
I'm really happy with the way Craig approached the dyno session. I wanted to see big numbers from the very beginning, but he sensibly crept up on the tuning side of things. Instead of taking home a pile of detonated, melted metal in a box, I took home a motor that's making over 800hp at only 6000rpm with a super-safe tune-up. It should last me a long time, and in something the weight of a Cobra, will certainly keep me entertained for a while! None of the engine dramas were caused by Craig, and I really thank him for having the patience to persevere through my troubles.
Thanks mate. The block is a 4 bolt SVO 9.5" deck height with the smaller Clevo 2.75" main journals. In the 800s back when the engine was built (2002!!!) was pretty decent power for a street motor, but the new turbos and bigger blowers are making 1400hp pump fuel small blocks possible these days...
Here's a crappy video of it, complete with distorted and out of sync sound, but the glowing pipes look pretty
Cobra Make, Engine: Venom, BF XR8 260kw, 6 speed auto
Posts: 158
Not Ranked
Quote:
Originally Posted by 750hp
Thanks mate. The block is a 4 bolt SVO 9.5" deck height with the smaller Clevo 2.75" main journals. In the 800s back when the engine was built (2002!!!) was pretty decent power for a street motor, but the new turbos and bigger blowers are making 1400hp pump fuel small blocks possible these days...
Here's a crappy video of it, complete with distorted and out of sync sound, but the glowing pipes look pretty
I dunno if I want 1400hp in a 1300kg Cobra! HAHAHAHA
Craig, put it back in the cobra!! I still vividly remember the spin around the back of Sanctuary Cove and only hitting 63% throttle position!! By far the fastest Cobra I've been in and the inspiration for my setup.
If we could have club registration in Qld for Cobras, I'd do it in a heartbeat. As it is, I'm having a hard time justifying the $1017 annual rego for a Cobra when the XY, Chevelle and Comet are only $180 each.
Still deciding...but yeah that motor sure was fun in the Cobra!
I don't remember it being such a drama...!
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