New Forza; New Year; First Challenge

[Spiny Anteater]

Just to add my twopenceworth on the cams debate...

For me, the question of to add cams or not to add cams is decided by the shape of the power curve. For example, last night I was building up an '87 Firebird which had a decidedly humpbacked power (and indeed torque) curve. By adding in an upgrade to the cams (I was going to try a two-stage upgrade but it ate too much PI), the power curve flattened out a LOT at the top end (if anyone has this car, have a look at the change in the upgrade shop). That meant that I would be operating at or close to my peak power output over a wide rpm range for longer than without the cam upgrade and to me that is a bigger plus than just a higher peak power output.

Oddly enough, I've also seen a similar effect at the opposite extreme with the high revving Toyota engines (and no doubt Hondas when I get around to tuning them). Again, adding the cams upgrade widens the peak and means I can stay on the "power cam" in a twin-cammer for longer.

In contrast, the SEATs have a very flat torque curve which in many of them edges downwards slightly as the rpm rises. This in turn gives a good power output over a wider power band. In such circumstances I feel that there is more to be gained from raising the whole power band rather than just the top end as with the cams. As a result, on a car such as the Cupra, the cams are probably the last engine upgrade I'll look at (along with the turbochargers). Of course, that's just my thinking. Others may disagree.

[Fit4aking]

Spiny - I just finished a build up and toon of a B-class Trans Am and found that the only way to increase the cars speed number significantly was to add the cams.  I didn't even hesitate due to the gobs of torque the engine still produced and I have to say that the car is a world different now.  Open had a shot with it around Laguna and I think he liked it a bit and was very close to his personal best IIRC.  Cams in a peaky, non-torque engine is generally a waste for me, I prefer to add torque to those little whiz-bangs to help them pull out of turns and shift less!!

[Blooze]

I agree with both of you 100% and should probably been a little bit more specific with my "Protect the Torque" speach.  As a case in point, the Saleen that I recently built out got a cam as the very first performance part added.  A high but peaky torque curve at a low RPM can be just as bothersome as an engine with low torque.

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[barumba]

Thank you all so much for taking the time to build, tune, test and comment. I'll take all under advisement. Sitting down to dins right now. Will apply your suggestions, feel her out, and reply accordingly.
Thanks, and Cheers!

[Blooze]

You are more than welcome Barumba.  That is the purpose of these little challenges, to share, discuss, perhaps even argue a bit, as well as educate.  Without that, it just becomes another hotlapping contest and who needs that?

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[barumba]

Your camber settings look about right but I always check these at the end of tinkering about with these type of settings. What I look for is similar amounts of difference in temperature between the front tyres and the rear tyres. On a circuit track the temperature on the outside wheel is hotter than the wheel on the inside. Then the inner wheel inside edge should be hotter than the outside edge by about 10-15 degrees. The outside wheel should have a hotter outer edge than the inside edge also by about 10-15 degrees. The difference in temperature of the front wheels should be about the same as should the difference between the rear wheels.

First off, for test tracks, I use Maple Valley Long, finding that there is a good variety of straights, elevation change, hair pins, sweepers, off cambers, and high speed breaking opportunities.  Enough to strive for even as possible temps across all tires. This is where I tune for grip. After running about 3-4 warm up laps, I open the Telemetry. First order of business is to check tire pressure. I adjust to get the 32-33# range, then every tune I save has 32-33# all corners. Then I look for temps. I have made this a priority. I adjust the cambers to yield even, flat heat profile across all tires. I look for 3-5* on turns and straights. Some hairy turns increase the delta to up to 10*, but I look to minimize that if I can. Then I adjust the ARB to yield even temps from side to side. These are all of course variable depending on the left, right combinations on any specific track. But, when I am finished adjusting for pressure and heat, I get 32's all around and (+/-) 3-5* left-right. Now, depending on the weight distribution, there will be more or less front to back. When I am done, I have laid down as much rubber as possible. The even heat profile across the tires = more rubber to the tarmac= better traction. Then I tune for balance. That is where I get scary.

I would also try different engine upgrades to see if you can find the best upgrade to apply. I don't fully understand the engine upgrades but I play about with the parts and watch the clock when unsure. I know the cams mess with the rev range and for some tracks/cars this can produce good results. As I understand it the higher reving is good for high speed tracks or tracks where the car is using the top end of the engine for large proportions such as speedway or Maple Valley where there are not many low speed corners. What we are looking for in this challenge is good acceleration at low speed and top end is less significant.

I might be off the mark but torque not hp is important here and cams might not be the best upgrade to choose. I started out by avoiding cams for the above reason but pretty much any of the other engine upgrades are good for torque. From memory I ran low 60s at Tskuba full. Then I took those upgrades off added the cams and compared times to see the difference. It didn't feel as good to me and I think the time was about the same. I then tried a few of the turbos to see if those proved any good. When I added the cetrifugal supercharger my time came down to 59.5 and I was pretty consistently under or around the 60 mark. I didn't bother to mess with any of the other upgrades after this as I knew it was going to be about as good as I was going to get from this car.

I replaced the sport cams with race fuel and sport ignition. This changed the TQ from 233 to 250 (much improved) and HP from 270 to 269 (not significant). More importantly, the TQ came in at 2200 RPM instead of 2600, the HP at 5700 instead of 6400. And the red line dropped from 7000 to 6500. So I think I have  taken care of the TQ issue. And, put the power in a range where the engine does not have to bust a gut. I have always found that adding TQ is superior to adding HP in most circumstances. I have found that the most TQ impact comes from Cams. If that is the last bit of PI I can add and stay in class, that's what I do.  BUT, apparently, that is not always the case, not so simple it would seem. So moving on, I will pay more attention to the benefit that the Cam upgrade has, and compare it to other available modifications before I save the tune. Lesson learned.

Thanks, Silvo 1981, for you advice.

[Silvo 1981]

I've not got my head round the cams upgrades yet myslef but I am acutely aware that it is the one upgrade that completely changes the feel of the engine. I watch the clock to see if the engine upgrade has a positive affect on the build and if not it is out and I try another combination of goodies.

Sounds like you're doing the right things on the tyre temps. Perhaps Maple Valley isn't the best track for this challenge though. I tend to use one of the Quick Rank Tracks depending on the type of track I'm working towards. Then once I'm in the right ball park on the QR track I tune for the track I'm working on. It seems to have worked well for me on this challenge but I am no hotlap guru. I think in this one instance I have just picked a good car and put in my fair share of runs with it.

Anyway glad to have been some help to you.

[Spiny Anteater]

First off, for test tracks, I use Maple Valley Long, finding that there is a good variety of straights, elevation change, hair pins, sweepers, off cambers, and high speed breaking opportunities.  Enough to strive for even as possible temps across all tires. This is where I tune for grip. After running about 3-4 warm up laps, I open the Telemetry. First order of business is to check tire pressure. I adjust to get the 32-33# range, then every tune I save has 32-33# all corners. Then I look for temps. I have made this a priority. I adjust the cambers to yield even, flat heat profile across all tires. I look for 3-5* on turns and straights. Some hairy turns increase the delta to up to 10*, but I look to minimize that if I can. Then I adjust the ARB to yield even temps from side to side. These are all of course variable depending on the left, right combinations on any specific track. But, when I am finished adjusting for pressure and heat, I get 32's all around and (+/-) 3-5* left-right. Now, depending on the weight distribution, there will be more or less front to back. When I am done, I have laid down as much rubber as possible. The even heat profile across the tires = more rubber to the tarmac= better traction. Then I tune for balance. That is where I get scary.

I'd agree with Silvio that MVL is probably not the best test track. It really does rely on a car having a good top end speed without sacrificing grip, but the lack of slow corners means that the losses of a poorly accelerating car are minimised. On most other (non oval or Le Mans) tracks the acceleration rating is one of the most important. It's no use having a great top speed if your car can't get near it by the end of a long straight. And while it's good to have lots of grip, if you can't pull out of that tight corner you blitzed the opposition on, they're going to come straight back past you on the next straight. If you really want a Figure of 8 track, I'd suggest Suzuka would be a better bet, even if it is quite long. Personally, I tend to use Catalunya National as my test track as it has a mix of everything; the only downside being that tunes there do tend towards oversteer (while a tune for MVL probably tends towards understeer).

CatNat isn't a Figure of 8, but I generally try to get the outside (left) tyres to have balanced temps across them with the inside being slightly warmer (say about 3-5 degrees F like you). I want the inside to be slightly warmer as with negative camber the car will be running on the inside of the tyre down the straights - if your outside tyre is perfectly balanced temperature wise, that suggests to me that the tyre is rolling over a bit on the corners.

Finally, a note on tyre temps. There seem to be a few schools of thought on this, so you could be just as right as me. However, I've found that the best pressure for stock and street tyres is 30-31psi with a noticeable drop off above 33 degrees. With slicks I generally aim for 31-32psi, and I haven't tested the sport/DOT's enough to fully decide on an optimum temperature. But, as with most aspects of tuning, a lot of this is personal preference. There is no right tune, but there are a hell of a lot of wrong ones (many of them mine )

[barumba]

Thanks, guys for taking the time and offering your advice. Blooze, I was able to save a couple of seconds with your tune on FK Down, but have not been able to see any improvement on FK Up. My driving for sure.
No matter, I have learned some valuable tips.
Thanks again to all.
Cheers!

[Blooze]

Well, it looks like this one has run its course.  I hope everybody learned a little bit from it - both tuning and driving FWD cars, but keepin' it 'tween the fences while runnin' up and down Mount Kaido.

We'll come up with another tester here in a couple weeks.  Don't want to turn these challenges into a job now... do we?

A real quick vote here - there were only a few liveries presented (Spiny's is in his Yellow Book thread).  Do we want to vote 'em up here, start a "poll" thread, or let it slide for lack of interest?

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[barumba]

I'm looking forward to the next challenge. As for liveries, I enjoy seeing them, but on this thread my attention is to the tunes. Maybe, a separate thread, linked or referenced from this (the next) challenge. I only have so much time on the 'box, so tuning and racing is where I spend most of it. But, I do from time to time like a diversion and try to decorate a car.

[Choccy]

I've not got my head round the cams upgrades yet myslef but I am acutely aware that it is the one upgrade that completely changes the feel of the engine. I watch the clock to see if the engine upgrade has a positive affect on the build and if not it is out and I try another combination of goodies.

Camshaft upgrades impact the timing and duration of valve travel. Basically, and as the summary in-game explains, you're impacting how fast the engine can complete a cycle(increasing RPM). The lobes on the camshaft of an OEM passenger car are designed for fuel-efficiency, clean emissions and then performance. For sports/performance cars, the priorities are shuffled.

Longer or shorter valve openings/closures affects how much air can be drawn into the cylinder and how much and how quickly (most of) it can be expelled. In any case, this kind of change has a significant impact on the characteristics of an engine and its output.

Consider the four cylinder engines in most of the JDM cars. The RPM at OEM spec is already high. The engine displacement is typically low. Upgrading the cams means you're making a high RPM engine spin faster, but at a point, 1,500 or 2,000 additional RPM fails to yield significant performance. This is where turbocharging or supercharging can bolster the bottom-line of a small displacement engine. If the engine is already spinning fast, then shift the focus of the build to making each combustion as efficient and potent as possible.

The V6s and V8s have gobs of low end torque. Large displacement. Stronger combustion stroke. Upgrading the cams extends the reach of these already heavyweight engines.

It's an oversimplification, but it might help explain why upgrading the cams on an American muscle car with a stout V6 or brawny V8 yields better gains than on a small displacement, four-banger. That said, a forced induction four-cylinder car can be a capable machine, but you'd be hard pressed to find the big power numbers attainable elsewhere.

[BarbecuePete]

I didn't get a chance to run in this one, but I just thought i'd add some thoughts on the cams debate...

Like Fit, I also added cams when I built up my B class '87 Trans AM, pretty much for the same reasons too, there was just no way of improving top end without adding the cams and flattening out that huge lump of torque makes it much easier to get the power down out of the turns.

I've also recently gone a bit mad with the Lotus 2-11, building it up in S class and then R3, the first upgrade I went for was the race cams as I wanted to build it up as an F1 style screamer. It was probably the best way to go too as it weighs so little lots of torque would just mean lots of wheel spin, I just wanted the raw power to hurl it down the straights.

On the flip side though I have an F Class Toyota 2000GT, I knew from Forza 2 that these cars have a good top end but don't have a lot of torque and struggle on acceleration, so when I was going through the build I decided to stick with the stock cam and add a turbo upgrade to improve mid range torque. As Spiny said, acceleration is probably the most important thing and if I added a cam it may have imporved top speed but it would accelerate so slowly that it would never reach it.