LS7 on the Dyno
Discussion
jellison said:Agreed, to a point. However, nobody has broken the code in the stock PCM yet. Someone will...and soon. But, until it's cracked and the programming software written, there is no other viable stand-alone solution except Delphi MEFI-4B which doesn't deliver granular programability.
The ECU on the vettes LS range is the NUT - Mega Millions invested in it by chevy - highly tuneable - After market ECU a total waste of time (IMHO).
In fact, it's yet to be determined that the stock PCM can run the LS7 in a stand-alone configuration. There are so many hooks to other inputs, there may be challenges trying to strip the extra information out.
I used to run my stack injection as Alpha-N. Alpha-N takes the throttle position sensor and crank position sensor to determine "load" of the engine. Its not the best way to do things, but for an all out race engine that creates very little vacuum its not such a big deal.
Speed Density uses engine vacuum to determine load. I converted to speed density, b/c I wanted better part throttle response. Fortunately, my engine and cam created enough vacuum to run it in Speed Density mode. I've spoken to guys who've run speed density with very little vacuum.
Cheers!
-Mack
Speed Density uses engine vacuum to determine load. I converted to speed density, b/c I wanted better part throttle response. Fortunately, my engine and cam created enough vacuum to run it in Speed Density mode. I've spoken to guys who've run speed density with very little vacuum.
Cheers!
-Mack
ezakimak said:91 ... the cheap stuff. I told them it would have to be 91 because that's all we get in Reno; California gas. Other parts of the country, they serve 93 and 94.
Builder, If you don’t mind me asking.
What was the octane rating of the fuel that was used when the engine was on the engine dyno.
Previous versions of LS2Edit will not work.jellison said:
I think Wortech have been tweeking the new LS2 ECU in the new C6 - presume same ecu?
Hi John, no not at all. I think the ls7 stuff is a whole new ball game hence why I think aftermarket mappable and 36-1 teeth is the way forward for the time being if you want complete flexibility?
Boosted.
Some folks here are changing out the crank reluctor and cam gear.
The new breed of LSx has a 58-tooth (60-2) reluctor and the old LSx has a 24-tooth. Guys are taking the engines completely appart and mounting new crank reluctors and cam gears just so they can use an LS1 PCM. That's a fair chunk of work, but maybe worth it to keep the old PCM in the car.
This method will also work for stand-alone installs. But, it just won't be THAT long before someone cracks the new PCM and can offer something good. My guess is 30-60 days.
The new breed of LSx has a 58-tooth (60-2) reluctor and the old LSx has a 24-tooth. Guys are taking the engines completely appart and mounting new crank reluctors and cam gears just so they can use an LS1 PCM. That's a fair chunk of work, but maybe worth it to keep the old PCM in the car.
This method will also work for stand-alone installs. But, it just won't be THAT long before someone cracks the new PCM and can offer something good. My guess is 30-60 days.
Would you care to speculate what the output of the engine would be on a different fuel. In Melbourne, Australia we can regularly get 98 octane unleaded and a 100 octane stuff is rumored to be just around the corner. Having said that the lowest grade we get over hear is also 91 octane.
I was trying to compare the LS7 with other engines based on a power per liter ratio, and there are a lot of engines out their now that are around the 100hp/L mark, especially some of the Euro engines. I think the current BMW M3 is around that mark. Based on the 427ci or 7L capacity does anyone think that you could get around the 700hp mark by using better fuel and or spinning the engine a bit harder and faster.
Maybe what’s needed is a management systems that will allow a quick change in the fuel and ignition maps depending on the fuel in the tank, so come race or track day just fill the tanks and flick the switch and you would be off.
I was trying to compare the LS7 with other engines based on a power per liter ratio, and there are a lot of engines out their now that are around the 100hp/L mark, especially some of the Euro engines. I think the current BMW M3 is around that mark. Based on the 427ci or 7L capacity does anyone think that you could get around the 700hp mark by using better fuel and or spinning the engine a bit harder and faster.
Maybe what’s needed is a management systems that will allow a quick change in the fuel and ignition maps depending on the fuel in the tank, so come race or track day just fill the tanks and flick the switch and you would be off.
builder said:
Some folks here are changing out the crank reluctor and cam gear.
The new breed of LSx has a 58-tooth (60-2) reluctor and the old LSx has a 24-tooth. Guys are taking the engines completely appart and mounting new crank reluctors and cam gears just so they can use an LS1 PCM. That's a fair chunk of work, but maybe worth it to keep the old PCM in the car.
This is what I do but I don't dismantle an engine first. I build up from scratch which saves a chunk of time. Means I can spec the engine and choose the ecu
Boosted.
ezakimak said:
Would you care to speculate what the output of the engine would be on a different fuel. In Melbourne, Australia we can regularly get 98 octane unleaded and a 100 octane stuff is rumored to be just around the corner. Having said that the lowest grade we get over hear is also 91 octane.
I was trying to compare the LS7 with other engines based on a power per liter ratio, and there are a lot of engines out their now that are around the 100hp/L mark, especially some of the Euro engines. I think the current BMW M3 is around that mark. Based on the 427ci or 7L capacity does anyone think that you could get around the 700hp mark by using better fuel and or spinning the engine a bit harder and faster.
Maybe what’s needed is a management systems that will allow a quick change in the fuel and ignition maps depending on the fuel in the tank, so come race or track day just fill the tanks and flick the switch and you would be off.
Tuners have already got 655 bhp at less than 7000 rpm with a cam, retainer and piston change. A good set of ITB should get you there
G Man
The UK GM Dealer I use has recomended that I run my Vette on our 91 normal fuel. As Optimax and the like are higher than the stock ECU setup can handle, because there super Plus Pump Gas is only the same as our normal fuel. I have a friend who put Optimax in his C5 and it started to cause trouble, whe he took it for a service they repeated the same thing to him.. now runs fine on our normal fuel...
So LS7 on Optimax with cam exhaust and piston Mods looking good for 700 ish
So LS7 on Optimax with cam exhaust and piston Mods looking good for 700 ish
ezakimak said:As GMan said, with hardware changes, you can pull a lot of power out of the LS7. Unfortunaltey, our "Department of Transportation", our "gas guzzler tax", and our insurance providers are going to make it more challenging for car companies to offer engines/vehicles that have really big HP and really high top speeds.
Would you care to speculate what the output of the engine would be on a different fuel.
For example, I think the top speed for the new Z06 Corvette is quoted at 198 mph. How hard do you think it would have been to change a cam lobe and make enough power to pick up 2 mph?
Regarding higher octane, my logic might be way off, but... An octane boost, by itself, isn't going to effect performance. The way I understand it, increased octane has a lower combustion temperature at pressure, so the engine doesn't melt when you run higher compression components. Higher compression...bigger bang...more power.
Can't really change the compression with a computer in an LS7 (yet). But, as ezakimak said, one can change the timing and cause the spark to ignite the fuel when it is compressed more...closer to Top Dead Center. Doing so would cause a hotter burn and the higher octane would counter the temp (no pinging).
After the blather, how much HP would it gain from a timing change and higher obtane? My guess would be 7-8%.
Here's a pic of the LS7 on the dyno with the spun intake. More later...
This is what I thought it all meant!
Detonation or Pinging is the uncontrolled burning or instantaneous explosion of the air fuel mixture within the combustion chamber of the engine, one that is not initiated by the ignition system of the engine. This explosion causes a massive amount of heat; huge shock loads on the reciprocating components and can also cause failures of head gaskets, pistons, rings and other components within the engine.
When an engine is not pinging / detonating there is a slower and more controlled burn of fuel across the combustion chamber, away from the point of ignition which is normally the spark plug. To make more power you need to get the point of ignition ie the time in relation to TDC that the ignition system fires the spark plug – as close as possible to that point at which the detonation occurs.
The octane rating of the fuel I thought was its resistance to detonation, and therefore has an effect on the total amount of compression (=heat) that an air fuel mixture can withstand before detonating. This would seem to hold true for forced induction applications as well.
In a forced induction application more air would be forced into the chambers, and a corresponding amount of fuel would also be metered into the chamber to maintain an equivalent air fuel ratio as in a normally aspirated engine. Most forced induction engines seem to have a lower compression ratio to reduce the amount of heat that is generated during the compression cycle of the cylinder. Not sure how comparable the Air/fuel ratios and ignition timing measurements would be though.
Either way to make power I thought the basics were,
More air and more fuel = more power
Every fuel will have an ideal A/F ratio at which it makes most power
Getting the ignition timing closer to the detonation threshold will make more power
Detonation or Pinging is the uncontrolled burning or instantaneous explosion of the air fuel mixture within the combustion chamber of the engine, one that is not initiated by the ignition system of the engine. This explosion causes a massive amount of heat; huge shock loads on the reciprocating components and can also cause failures of head gaskets, pistons, rings and other components within the engine.
When an engine is not pinging / detonating there is a slower and more controlled burn of fuel across the combustion chamber, away from the point of ignition which is normally the spark plug. To make more power you need to get the point of ignition ie the time in relation to TDC that the ignition system fires the spark plug – as close as possible to that point at which the detonation occurs.
The octane rating of the fuel I thought was its resistance to detonation, and therefore has an effect on the total amount of compression (=heat) that an air fuel mixture can withstand before detonating. This would seem to hold true for forced induction applications as well.
In a forced induction application more air would be forced into the chambers, and a corresponding amount of fuel would also be metered into the chamber to maintain an equivalent air fuel ratio as in a normally aspirated engine. Most forced induction engines seem to have a lower compression ratio to reduce the amount of heat that is generated during the compression cycle of the cylinder. Not sure how comparable the Air/fuel ratios and ignition timing measurements would be though.
Either way to make power I thought the basics were,
More air and more fuel = more power
Every fuel will have an ideal A/F ratio at which it makes most power
Getting the ignition timing closer to the detonation threshold will make more power
andygtt said:
My understanding is that the European measure of octain is different to the US, so 91 is around 97-98UK..... does anyone know for sure.
The reason I think this is that my AS engine was dyno'd on 91 octain and I wondered if running on 98 would make any difference.
US uses AKI which is a combination of RON (Research Octane Number) and MON (Motor Octane Number) which are two different ways of measuring the fuel rating. In the US lowest fuel rating (regular) is 87 AKI (92 RON), mid grade is 90 AKI (95 RON) and premium is 93/94 AKI (98/99 RON).
Your AS engine on 91 Octane is probably run on UK 95 RON, if the ECU is 'intelligent' and can adjust itself for different fuel ratings then yes you should get a slight benefit from using super-unleaded instead. If it cannot adjust itself then no you will not get a gain.
andygtt said:
My understanding is that the European measure of octain is different to the US, so 91 is around 97-98UK..... does anyone know for sure.
Have a read at this: http://en.wikipedia.org/wiki/Octane_rating
It'll tell you, or link to, more that you could ever want to know on the subject.
Basically 91 US octane rated gas (which is what we're supposed to run our AS engines on) is the same deal as standard 95 octane UK unleaded.
andygtt said:
The reason I think this is that my AS engine was dyno'd on 91 octain and I wondered if running on 98 would make any difference.
When I took my car to a chassis dyno I actually managed to do back to back runs with Optimax and stock Safeway unleaded. There was no difference. Optimax also didn't cure the part-throttle 1500 rpm pinking my AS engine has suffered from new (until I replaced the dizzy with an ECU)...I think they were a bit over eager on their advance curve (as well as not fitting vac advance...
). Basically unless you have the engine set up for high octane US race gas or in the UK on Optimax then it's a complete waste of money to use Optimax in a normally aspirated Chevy. IMHO.
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