Project VF Boosted Part III - THE CAM...
Well as promised we are back with a new change. In PVFB The Cram we hinted we were going to get a larger cam into the Blown Beast. Well first we thought we had better get it onto a hub dyno for a definitive baseline. The SQP DD roller was starting to battle with the output and was vague in seeing any real data on upgrade outcomes.
So as it raced last time at The 'Plex we bolted it onto Shannon at TuneCorps independent hub dyno. We not only get none slip data from this but also remove any shadow of doubt as to the power output of the ute. It isn't our machine and Shanon is the operator. Total transparency. As a side note- thank you to Shannon for making his machine available for this and his support. it is truly great working with other like minded shops who are interested in the integrity of data and outcomes.
On the SQP DD machine we saw just north of 800rwhp with a lot of slip. We also had it on the dyne pre drive upgrades. So what did it put to the hubs??
It is interesting that what we learned on the strip with the blower drive has translated to a nice increase in boost. Previously we had just over 19psi. Sorting the drive out and removing the flex in the idler has seen that increase to just on 20psi. But how is the power? The little standard stroke LS3 is putting just short of 900hp to the hubs. 892hp to be exact. Independent dyno- independent operator- independent result.
Cam is IN!!
So where are we going to go with the cam? A tried and true step up in the SQP range is the SQ60. This cam was developed over many years for our large cube LS3 based 416 stroker builds. The SQ53B is in the lower 220s@ .050 on the intake. The SQ60 steps well into the 230s. The SQ53B PROVES clearly you don't have to cam the heck out of these combos if you have your valve events in the right places. So with a lot larger cam going in...how are we going to stop boost robbing over lap from increasing. Those switched on will know the answer here....Lobe Seperation Angle-LSA. The same thing that gives chop at idle will hurt boost and power in the little engine. The larger cubed engines soak up cam like water on sand. It will be interesting to see where a wider LSA bigger cam will take it and where it will gain/lose.
So without posting a bunch of cam install pics it is onto the hubs again for a baseline tune. The result?? We gained!!
The little donk loved it! How is that for a pick up on an engine already putting 890 odd to the hubs?? Not only a 22hp gain at peak but a gain ALL the way through the rpm range! As much as 30hp in the lower rpms and it carries power longer as would be expected with a longer duration lobe giving more time to get charge into the cylinder. We were cutting it off at 7200rpm but it was still carrying! 914.9hp and holding! Great valve train control right there. Peak torque is UP by 32lbs. But have a look at BOOST! It is also up but at LOW rpm where overlap from larger lobes should of killed if LSA hadn't corrected. Longer valve event has helped there also. Very pleased with that outcome and it reinforces what we have learnt with getting valve events right on LS engine platforms. Engines are a complex item and moving air is very hard to quantify with so many dynamic forces in play.
Here is a fun fact- .we have used the same hub dyno for several cars now. Here is the thing that shows that moving air through an engine is the secret to making power and not fluffing over how much boost the power adder is pushing. All the following with SQ60 camshaft. PVFB- 378cube- 20psi- 892hp. LS3 416cubes MAST MIDS 16psi- 890hp. LS7 414cubes- MAST- 14psi- 896hp. ALL WITH SAME BLOWER SPEED!! I think nothing shows moving air through the engine results in power not boost on its own any better than those results right there.
One of the hardest things to quantify and show it the changes in density of air and the effects of pressure and temperature on air density. We know temperature is a major step in density changed but pressure (boost) also impacts it greatly. The temperature rise from compressing air is relative to the amount the air is compressed but it is also effected greatly on the temperature of the air coming in. So atmopheric temperature air into the charger is paramount in it's importance. Trying to remove heat from massives volumes of air being pumped through the engine is a monumental task. Keeping the air into the blower as low as possible is the best 1st step. The OTR on a Harrop blower does this well. To the point where we see an extra pound of boost running down the track from the ram air effect into the blower. Blower efficiency is also critical to the movement of air. Too much speed on a small capacity blower may see similar boost levels but not the same power gains from boost as it is no longer moving air efficiently and isn't increasing density. We haven't seen that with a 2650 yet. But nearly everyone has with the LSA 1900 blower. Everytime we have stepped on boost with the 2650 we have found power. In this case we moved more air through the engine and pressure rose! With the complexities of the models needed to illustrate density pressure relationships, we brought in a highly respected mechanical engineer in the engine development field. Yep...we phoned a friend. "Hey mate...need to quantify some science on air density. Can you do us up a spread sheet so we can run some math?' "Leave it with me was the reply"...why do we need a spread sheet?? Here is the math...
What does it show us?? OK all science on fuel is in mass. GM even use weight of air in their ecu calculations. You are combining the weight of air and the weight of fuel (ever wondered why injectors are rated in lb/hr?) to give a balanced chemical equation making use of all the oxygen available to burn carbon expanding gases to create pressure in the cylinder rotating the crank. What did the math show? In summary that air density (taking the blower has the efficency to be able to increase boost without compromising density) changes as follows by the effects of temp... if temp rose from 40*C to 85*C it has the same effect on density as going from 20psi to 16psi. Basically the density gains in weight of air produced by pressure are lost to temperature. That is air measured at the port mouth. But what happens when that charge is injected with a copious amount of alcohol and that alcohol changes in state from a liquid to a gas? What do we see in temperature after this has taken place? Time for a longer temp probe in the manifold to take some readings and see where our density lobs? We all know that hot air is prone to detonation in a boosted application. one very basic principle of engine compression ratio is to raise the temperature of the charge to a point where it is easy to ignite. Think of a diesel engine- it takes in plain air, the cylinder compresses the air to the point that the temp of that air is high enough to combust the fuel that is injected directly into the cylinder. Great with a diesel as they time that injection to make sure the crank angle is correct and the rise in pressure from the combustion of the fuel drives the piston down the bore. With a spark ignition engine if the charge get to the point of it self igniting before the ignition system fires it, the crank angle can be at a point where the exanding gas induced pressure rise can't turn the crankshaft resulting in high cylinder pressure and failed parts. How do you lift a head? Exactly as written there. So it is not only imperitive to control intake temps for charge density but also to keep control of engine management. But here is the rub...remember compressing to the point where it is easy to ignite? Well colder charges need more timing advance just as hotter need less. There is a window where we have great control and latitiudes. Engine design, fuel type, intake charge temps, camshaft design and compression ratios are all key pieces in the combination of factors that cotribute to the success or somewhat failure of any engine combination. If you have charge temperature rising during the pass the density of air is changing and fuel delivery needs to be compensated for in the control system. No different to spark advance. Nice game hey? To calibrate to a rock steady AFR whilst dealing with the variations in density and changes in temperature is a complex task that can't be achieved by hacking commanded AFRs and the likes. Then you have to deal with variations in load on the engine as it runs through the gears and humidity in that intake charge and its effects on combustion speeding or slowing the burn...and they wonder why we spend so little time on the dyno and so much at the track.
Anyhow- Enough of the white coat science boring stuff before they come and take me away hey Alexi?! Lets get it to the track and spin some tyres. We have had it down for a couple of test laps to scrub up the tune in the real world- we got the data. How did it go? Well we spun the wheels heaps and pedalled it like MOFO but indications are good- fastest speed it has gone with heavy driver even with a pedal! Back soon!!
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