Project VF Part III - Let the CAM's Continue
Project VF Part III - Let the CAM's Continue...
Stage II SQ54
With the weather beating us to death by stealing our available track days we got the Stage II SQ54 cam into Project VF. What is the SQ54? Way back in 2002 when we were first developing the LS1 engine and Kim Stevens' 382 LS1 VU Ute was the fastest in the land running 11.02@ 123mph N/A we used a Comp Cams custom based on the XER lobes that was 232/236 with .580" lift. As a blast from the past, I found this link to a dyno day from '02...
Based on the drivability of this engine and the power it made we updated it to the SQ54 for use in GenIV engines. It is as tight on piston to valve as we are prepared to go with reliability and the customer's engine life in mind. GenIV engines don't have valve reliefs from the factory. This limits how much lift at top dead centre with a safety margin of .080" on the intake and .120" on the exhaust can be squeezed in there. We don't subscribe to machining valve reliefs into assembled engine method nor allowing the engine to machine it's own via interferance with the piston. Yeah we see it!! All good until it breaks and then the "first time we have seen that" excuse runs out. So with respecting the customer's property (ENGINE) in mind and leaning to the conservative side of safety the valve events of SQ54 are the max we recommend and will fit guaranteeing reliability.
So covers off again and into it!
Lubed and ready for insertion...
PAC Beehives removed and locators with new seals installed. Dual spring kit is considerable more work but with the higher duration and rpm potential...duals are a must..
Dual springs with Titanium retainers...locked and loaded.
What I consider the most crucial and least understood part of the install...lifter preload. I could write a novel on the dos, don'ts and implication of getting it wrong but will condense it to "it has to be right and serves more than keeping the valve train quiet!" With a nonadjustable OEM rocker, the pushrod length sets the crush.
To quote some AC/DC..."for those about to rock...We Salute You!"
After fitting the SQ54 and spring package to match, it was onto the dyno.
After careful ECU calibration, above is the result...a gain of 20rwhp. As can be seen from the graph, the increase in power is at a higher rpm and after the peak of the SQ53. What this will translate into on the track is hard to quantify as power above the SQ53 peak is only increased by 15hp and seeing as the engine spends most of its time away from where the increase exists we will have to stab it on the track and find out.
But winter intervened and we have had a few months lay off. We finally had the time to get it to the track on re opening. New season, new enthusiasm.
Well it may look like it went slower or there was no gain at all but that is not correct. The best we got from the SQ53 in comparable conditions was 11.89@116.27mph. Using the old power/speed calculator, an increase of 10hp average is shown. Dyno showed 20hp...track confirmed 10hp. What went wrong? I think it is safe to say that the increase at comparable rpms is more to the point. The SQ54 carries power longer and peaks later via it's extended valve openings...longer duration gives you more time to pull it in and out but it also moved the power curve later. Maybe extending the shift points some in the trans would of seen us average another 5hp but bottom line is the increase is more top end orientated rather than daily driver. I believe it clearly illustrates what I tell customers about cam design...stop concentrating on peak power. To choose a cam by its peak power output is a mistake. Sure the SQ54 improved the car but it comes with the introduction of cam surge...with the converter in Project VF it isn't evident but at 1800rpm in a manual car a slight surge can be felt. Not a big issue to most but it just isnt as nice as the SQ53...
Iam sure if we had optimised the converter, added more rear ratio and moved the shift points higher as a dedicated SQ54 package we would of dropped another .1 second but I don't want to get bogged down as we have other fish to fry. End of the day is the SQ54 is quicker and faster than the SQ53. Validating the SQ54s improvement is that over 6 laps it never went slower than 11.84.
SQ57 Arrives! Do We have A New Stage III?
So where to now? For interest I installed the cam I had in mind to start the Project VF MAST 4.0 head upgrade with I have planned. Now this thing is a grumpy unit that we had great success in the 6.0L racing classes over the years with these lobes even coming second outright in the Australian Off Road series Pro Class against all the turbo wizz bang pop pop powered machines proving you don't race dynos... Revised for road use rather than off road, we designated it the SQ57. Seeing that the MAST heads have so much free drop on the valves, we don't have to stress out too much on the piston to valve issue. Needless to say on the OEM head is it tight...so out with the SQ54 and in with the SQ57.
Now not the only thing to change at SQP over winter was the season...after 12 years with the same dyno the opportunity arose to update from old faithful to the latest and greatest that Dyno Dynamics have to offer. A deal was struck and my old friend was sold. It would seem weird to some reading this but when you have operated on the same machine for so long, you become very comfortable with what it is showing you and how it is going about it. You get numbers coming from it that you can trust as they have proven to be reliable. So in with the new dyno. Digital and wireless too!
With the change of test equipment, a new baseline needed to be established...
Well that looks about right to where we were with the old machine allowing for a 2% window of accuracy...it actually comes in under 1%...
So with the SQ57 installed it was onto the dyno for some ECU recalibration and comparison to the SQ54.
So clearly a nice increase across the rpm range but lost some under 3500rpm. For years I have tried to show customers that bigger and bigger cams might make you more at peak but they come with compromises and challenge them with "how often are you over 3500rpm?." Some of the compromises are drivability issues. Some are where they lose low end power. Worst compromise of all is reliability issues caused by aggressive profiles with marginal clearances. SQ57 is a cam that I have resisted offering for everyday use other than stroker engines where the increased displacement makes up for losses in low end torque. This is even though I know its power protential but can now make a case for it in auto cars where the converter masks the low end power deficit and cam surge. Also with an auto we can control the rpms it will see and there for minimise the potential for piston and valve interference which is well inside of the margin of safety we adhere to. It will be real interesting where it takes us...the track will decide.
Stage Three It Is!
9/10/14
We got Project VF to the track Wednesday for a look at where the SQ57 got us to. We are pleased to say that the gain of 2mph on the 3900lb barge plus driver that is the VF SSV backs up completely what we saw on the dyno. Black track shows us an increase of 25hp. Dyno showed 20hp so that is close enough for us to say PROVED! It once again shows the real value of the dyno as a before and after measuring tool. The biggest misuse of dynos today is the sale of horsepower...most shop until they find the highest HP/$$ without bothering to question why the numbers are so high. Big mistake!
and to prove the mph was real...
The most interesting thing with Project VF to date is it is proving that peak power is accounting for very little in the street car scene. The power at peak is improving and we are up 35rwhp from where the SQ53 was but the car is ETing very similar having only improved by 2 tenths. What we are seeing clearly is the result of no real extra power under the curve. Sure we are increasing at peak but power where the converter is trying to move the lard arse off the line isn't changing substantially enough to impact the 60' times. In fact all the gains so far have been in the second half of the track. It clearly proves what I have shown customers for years...if we want to increase power at lower engine speeds, we either have to give it some cubes or push some air in to it with a positive displacement supercharger...you want to move weight, you require more force. You want to make more force, you need more air in the cylinder. The other method is to loosen the converter up and gear the heck out of it and get it in the fat part of the curve. We won't be doing that as we are trying to develop a fast street package...not a loose as a goose, high revving race car that won't cuise in comfort...
But back to where we are with the 6 litre. Clearly bigger and bigger cams are moving more air into the cylinder via longer valve openings but we are at the point of deminishing returns now. The cylinder head is limiting the amount of air that the engine can move. So we reckon it is time for some MAST 4.0 cylinder heads! The aim will be to throw them in the mix and add some airflow that isn't coming from larger and larger cams taking away the drivability and street functionality of the vehicle.
Check out these babies!
Next we will document the fitting of these bad arse heads from MAST along with parts required to set up the valve train. See you soon!
<< Project VF Part II - Let the CAM's Begin
Project VF Part IV - The Need For Speed Continues >>
