Britcar Silverstone 24Hr Race - 1st/2nd October
Discussion
macgtech said:
Indeed - the heat should be straight forward to solve (!), though the misfire was certainly down to fuel starvation; numerous other teams running LS7's were struggling with exactly the same symptoms as ourselves - some with far more dire consequences than we had. Going to investigate it further but it seems we need to be looking at common factors - maybe the fuel.
What type of fuel surge tank did you run? Was it the factory external tank with the LP pump? Did you have any surge tanks inside the fuel tanks? Were the fuel pumps submerged?
SchimmS said:
What type of fuel surge tank did you run? Was it the factory external tank with the LP pump? Did you have any surge tanks inside the fuel tanks? Were the fuel pumps submerged?
We run the regular LP and HP setup, and the factory Swirl Pot. The pumps have been relocated into the side pod for ease of access.macgtech said:
We run the regular LP and HP setup, and the factory Swirl Pot. The pumps have been relocated into the side pod for ease of access.
Hi Jonny,Sorry I missed you at the weekend
Just a thought re. the pumps, if they're in the side pods are they in any decent airflow? Given the high ambient temps at the weekend, surely excess temps would be the biggest suspect for the fuelling issues?
A valiant effort though and keep up the good work!
Hi Jonny,
Sorry to hear about that frustrating weekend.
I suffered the same starvation problem in the past running the car at the track during the spanish summer but I have solved it with the cooler+heat barrier for the pumps and a bigger LP pump (with the previous LP pump, fuel was too much time into the surge tank exposed to heat). I'm surprised if other teams had suffered the same...mmmmmm.. :/
Don't worry, I'm quite sure to see you again with better results.
Cheers,
Javier
Sorry to hear about that frustrating weekend.
I suffered the same starvation problem in the past running the car at the track during the spanish summer but I have solved it with the cooler+heat barrier for the pumps and a bigger LP pump (with the previous LP pump, fuel was too much time into the surge tank exposed to heat). I'm surprised if other teams had suffered the same...mmmmmm.. :/
Don't worry, I'm quite sure to see you again with better results.
Cheers,
Javier
Edited by srreck on Tuesday 4th October 09:05
What a frustrating weekend! You know you can be competitive at the front of the grid but you spend all the time fixing problems.
One of the problems with the design of the Ultima is that the exhausts exit though an opening to the engine compartment. When measured statically some of the engine noise is also picked up by the meter.
Mosler manage to meet the noise levels with the same engine in a similar position so it is do-able.
The fuel temperature issues raise their ugly head again. I know it has been warm but it is often a lot hotter at races in the southern states of the USA - the home of this engine.
It seems that pumping, at high pressure, the amount of unused fuel over a hot engine and then passing it through a restriction and back to the tank is the problem. Can someone please tell me why this is necessary?
Why not fit the pressure relief on a tee just after the HP pump and blank the return from the fuel rail. If you fit your fuel pressure sensor at the end of the rail you can check that you have sufficient pressure at the injectors and adjust the regulator accordingly.
The fuel returning to the tank would only be heated by the pressurisation process and not the engine heat. You could still cool it via an air-to-fuel cooler to ensure the fuel getting to the rail is as cool as possible. The only possible problem will be at start-up of a hot engine when the fuel in the rail will have had time to vaporise, but that should be only a temporary problem until the engine catches.
Your thoughts please.
Paul
One of the problems with the design of the Ultima is that the exhausts exit though an opening to the engine compartment. When measured statically some of the engine noise is also picked up by the meter.
Mosler manage to meet the noise levels with the same engine in a similar position so it is do-able.
The fuel temperature issues raise their ugly head again. I know it has been warm but it is often a lot hotter at races in the southern states of the USA - the home of this engine.
It seems that pumping, at high pressure, the amount of unused fuel over a hot engine and then passing it through a restriction and back to the tank is the problem. Can someone please tell me why this is necessary?
Why not fit the pressure relief on a tee just after the HP pump and blank the return from the fuel rail. If you fit your fuel pressure sensor at the end of the rail you can check that you have sufficient pressure at the injectors and adjust the regulator accordingly.
The fuel returning to the tank would only be heated by the pressurisation process and not the engine heat. You could still cool it via an air-to-fuel cooler to ensure the fuel getting to the rail is as cool as possible. The only possible problem will be at start-up of a hot engine when the fuel in the rail will have had time to vaporise, but that should be only a temporary problem until the engine catches.
Your thoughts please.
Paul
[quote=Storer]
It seems that pumping, at high pressure, the amount of unused fuel over a hot engine and then passing it through a restriction and back to the tank is the problem. Can someone please tell me why this is necessary?
Not quite sure I understand - the LS7 fuel rail is set up with just an inlet - fuel doesn't pass through the fuel rail and return to the tank.
I am also having trouble understanding this problem with you guys running in the UK. Global warming must be really having an effect in Europe! I run a GTR in the Silverstate race in Nevada, and track the car in Southern California in the summer and I have never had this problem with fuel vaporization and/or heating.
I am running fuel cells, and connected the bottom of both sides together, so I pull off them simultaneously. I pull off of the bottom of the fuel cells through the LP pump into the swirl pot. HP pump pulls off the bottom of the swirl pot, through a 100 micron filter, through the HP pump, through the 10 micron filter, to the regulator, and then to the fuel rail. Overflow from the swirl pot returns to the fuel cell.
Exhaust manifolds are designed to sit high in the engine bay so as to reduce as much as possible the heat to fuel, alternator, and A/C compressor.
It seems that pumping, at high pressure, the amount of unused fuel over a hot engine and then passing it through a restriction and back to the tank is the problem. Can someone please tell me why this is necessary?
Not quite sure I understand - the LS7 fuel rail is set up with just an inlet - fuel doesn't pass through the fuel rail and return to the tank.
I am also having trouble understanding this problem with you guys running in the UK. Global warming must be really having an effect in Europe! I run a GTR in the Silverstate race in Nevada, and track the car in Southern California in the summer and I have never had this problem with fuel vaporization and/or heating.
I am running fuel cells, and connected the bottom of both sides together, so I pull off them simultaneously. I pull off of the bottom of the fuel cells through the LP pump into the swirl pot. HP pump pulls off the bottom of the swirl pot, through a 100 micron filter, through the HP pump, through the 10 micron filter, to the regulator, and then to the fuel rail. Overflow from the swirl pot returns to the fuel cell.
Exhaust manifolds are designed to sit high in the engine bay so as to reduce as much as possible the heat to fuel, alternator, and A/C compressor.
k wright said:
Great point about relieving excess pressure and flow prior to sending the fuel to the rail.
Better still to only pump what is required which is why I am eagerly awaiting Max_Torques speed controller.It will drive the HP & LP pumps separately and only run them fast enough to meet demand so fuel will not be going round and round getting hotter and hotter.
Steve
deadscoob said:
Does that take signals from the ecu Steve? Is it something made himself or an off the shelf product?.....
It is a product he is developing himself. The PEC boards are made and he is finalising the software. It is self contained and does not require input from the ECU.Read the ongoing thread here.
Steve
Really sorry things didn't come together for you. however you deseerve a MASSIVE well done for gertting a untested car to an event like this and being up there with the best!
Obviously it looks like heat is a big problem for you guys at the moment. Have you considered coating / wraping the headers for the next event? Also maybe installing some heat sheilding maybe? sure you have though of both the above but its worth mentioning.
Also, are you happy with the amount of air flow through the engine compartment? I know the Noble guys have to do a few mods to get the air into and out of the engine bay.
THanks,
Chris.
Obviously it looks like heat is a big problem for you guys at the moment. Have you considered coating / wraping the headers for the next event? Also maybe installing some heat sheilding maybe? sure you have though of both the above but its worth mentioning.
Also, are you happy with the amount of air flow through the engine compartment? I know the Noble guys have to do a few mods to get the air into and out of the engine bay.
THanks,
Chris.
Storer said:
Chris
If you check the pictures of the MacG car you will see the headers are wrapped and they already have heat shielding in front of the fuel tank.
Jonny has said he thinks the heat issue can be solved quite easily so I will be interested to see what they do.
Paul
SH!T sorry, i should have looked at the pics a bit more closely! If you check the pictures of the MacG car you will see the headers are wrapped and they already have heat shielding in front of the fuel tank.
Jonny has said he thinks the heat issue can be solved quite easily so I will be interested to see what they do.
Paul
Still think that getting more air in and through would help. Not sure how easy it is to do though!
Chris.
Storer said:
Jonny has said he thinks the heat issue can be solved quite easily so I will be interested to see what they do.
Paul
More holes! We have some ideas to increase flow through the engine bay - and we also need to heatshield the tank better from the coolant pipes. Relocating the LH pipe to the RHS is also an option which will make a big difference - but may cook the driver!Paul
The first stage though is to get the gearbox out and upgraded/repaired, then to get the engine out and tidy up round the engine bay and get more shielding in their. Also going to re-plumb the fuel system slightly and relocate the regulator to get it out of the heat.
As they say, 'the best laid plans' and all that...
Also need to look at a brake upgrade if we get some funding in, as the disc cut through the calliper when the drive hub broke because of the constant jerking! Frustratingly all our issues are coming down to lack of testing - which was half the reason we entered the 24 in this our first season - we were always going to find ways we need to improve the car, so now we need to spend the winter resolving the issues and finding funding for next year.
Exciting times!
regulated pumps are a great idea but I can imagine make mapping more difficult as with a constant pressure you only need to map the time of injector opening, now you have a changing pressure and therefore injector opening is not only linear but having another parameter to be taken into account.
I know there is some that think that only the regulator after the fuel rails is the right way to do which is running a lot of fuel over the engine. My first idea would be to place the regulator in front of the rail and have it like the Corvette setup where the rail ends in a dead. So ony fuel that is actually consumed by the engines is sitting on top of it.
And as mentioned before do not forget the peltier elements that could attach to the swirl pot and electrically cool the fuel !
I know there is some that think that only the regulator after the fuel rails is the right way to do which is running a lot of fuel over the engine. My first idea would be to place the regulator in front of the rail and have it like the Corvette setup where the rail ends in a dead. So ony fuel that is actually consumed by the engines is sitting on top of it.
And as mentioned before do not forget the peltier elements that could attach to the swirl pot and electrically cool the fuel !
spatz said:
regulated pumps are a great idea but I can imagine make mapping more difficult as with a constant pressure you only need to map the time of injector opening, now you have a changing pressure and therefore injector opening is not only linear but having another parameter to be taken into account.........
My understanding is that the pump controller is using PWM and does not require a mechanical pressure regulator. It will in fact maintain an even more accurate fuel pressure across the power band and has a very fast reaction time against change in demand. Steve
I like the idea of "on demand" fuel pumps but there must be some element of fluctuation in fuel pressure if the pumps are triggered by pressure.
Is the idea to trigger the pumps by the ECU's signals to the injectors (with a small delay) as this may give a more consistent pressure.
The problem with "on demand" fueling is that the pumps are not designed to stop and, more importantly, start under load (pressure) sometimes many times a minute.
Paul
Is the idea to trigger the pumps by the ECU's signals to the injectors (with a small delay) as this may give a more consistent pressure.
The problem with "on demand" fueling is that the pumps are not designed to stop and, more importantly, start under load (pressure) sometimes many times a minute.
Paul
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