Before vs After CSL+ Spec Engine Build

[TomK]

I accept that the graph shows an increase below that too. Very odd how it dips around the 5-5.5k rpm range?

Mine with similar mods does this too, but it's interesting I guess that my peak torque is ~4700 vs this one at ~6300. That seems a bit off to me being that high up?

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[Ed Doe]

I accept that the graph shows an increase below that too. Very odd how it dips around the 5-5.5k rpm range?

Mine with similar mods does this too, but it's interesting I guess that my peak torque is ~4700 vs this one at ~6300. That seems a bit off to me being that high up?
20240127_212036.jpg

You guys are TERRIBLE - all this is doing is making me want Schrick cams and a naughty great airbox

Speaking of which, are you both running identical airboxes? Airbox volume will likely have an effect on the inlet harmonics, which can affect torque?

[TomK]

You guys are TERRIBLE - all this is doing is making me want Schrick cams and a naughty great airbox

Speaking of which, are you both running identical airboxes? Airbox volume will likely have an effect on the inlet harmonics, which can affect torque?

The airbox is essential, whether it makes more power or not you'll care not I guarantee!
I think I'm right in saying that I am the only car I know of running the goke csl airbox made for the z4m
The difference to others is that it locates directly to the Z4 air intake and seals on the slam panel. I imagine it helps, but some people seem to think the narrowness of that inlet will affect performance. My numbers suggest otherwise, but yeah, who cares, it seems to go well enough for my skills (i think im around 1350kg ish full fluids) and sounds/feels great!

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[GT Spec]

I accept that the graph shows an increase below that too. Very odd how it dips around the 5-5.5k rpm range?

Mine with similar mods does this too, but it's interesting I guess that my peak torque is ~4700 vs this one at ~6300. That seems a bit off to me being that high up?
20240127_212036.jpg

Hi Tom,

I wonder if it could be the 100 CPSI cats? Have you had your VANOS unit tested via ISTA? Strong figures though! Which rolling road did you use? I noticed they are also using the TAT software.

Cheers,
A

[TomK]

I wonder if it could be the 100 CPSI cats? Have you had your VANOS unit tested via ISTA? Strong figures though! Which rolling road did you use? I noticed they are also using the TAT software.

Cheers,
A

Yeah, that could be something robbing you a little lower down, I'm not sure really? I haven't seen an S54 plot with the peak that high up though.
I have the stock cats and headers. VANOS tested good. Dyno was a mustang here... https://www.regalautosport.com/tuning/v ... road-demo/
Enjoy, bet it sounds amazing roof down!

[///MBan]

Thanks for sharing, GT Spec. Your setup is just like my probable end plan. I have the same airbox arriving this week (which I'll get tuned by Severn) and I'm really debating the cams and final drive change. So, I have a few questions, if you wouldn't mind?

You say you have a full Super Sprint exhaust. Does this include headers?

Any insights into why you went for 288/280 cams rather than 280/272? On NAM3 the general consensus seems to be that 280/272s make about the same amount of power but more torque below the peak?

How do you like the 4.10 final drive?

It looks like your CS Sportstersnare upholstered in leather to match the Imola Red door cards. How did you find the right leather and get it applied? Any comments on the seat installation (rails, clearance, weight difference vs standard, etc)?

Maybe you should does do a build thread and I can soak it all up from there

Thanks!

[pokeybritches]

Hi guys, Josh the “mapper” here. This was an awesome car to tune, and OP was outstanding to work with and very thorough. Overall, it was a great experience, and I always appreciate the opportunity to tune such a fantastic setup. I want to weigh in on a few points to course correct based on my firsthand knowledge.

First, the dyno scaling exaggerates a “5.5k rpm dip” in torque. The torque only varies by about 3-5 lbft between 4500-6000 rpm, and it maintains a healthy +/- 3% between 4000-7800 rpm. Torque and rpm are both contributors to horsepower. Horsepower is felt as the shove of acceleration, and this car makes more power at 5.5k rpm than it does at 5k rpm due to the similar torque with increased rpm. This leads to strong, linear acceleration as rpm climbs.

As for what can cause a slight dip in torque, it can be any number of hardware factors such as intake manifold design, trumpet shape, airflow resonance as it enters the engine, or even run-to-run variation within the dyno’s tolerances. There is no untapped torque at 5.5k rpm with this setup- we made as much as the hardware allowed. After overcoming the unique challenges of tuning MSS70 for alpha-n, torque generally comes from improved airflow (VANOS), optimization of ignition timing advance, and fuel mapping. Once the parameters have been identified which can influence torque, the result of adjusting each of these parameters can be likened to a bell-shaped curve. The ECU will have optimal settings at each load and rpm where it makes the most torque, and changing each setting away from ideal in either direction will result in a loss of torque. In this case, we built the base tune from another Z4M with a similar hardware setup which we had dyno tuned extensively. We progressed through a further 15 iterations of tuning to confirm no additional power could be gained with timing or VANOS adjustments in either direction.

One thing to consider is the driver will never feel torque directly… only horsepower. By this I mean that an engine that is momentarily making 500 horsepower will provide the same shove to a driver regardless of whether the 500 horsepower is made by 1313 lbft at 2000 rpm, or 250 lbft at 10504 rpm. This analogy makes a few assumptions about each car’s equitability and capabilities, but the point is that the magnitude of the shove is determined by horsepower. If horsepower increases, so does the shove. This Z4M’s 14% enhancement in naturally aspirated horsepower will translate to a massive performance improvement.

I would caution about comparing numbers from different dynos, including those with an arbitrary correction factor applied to estimate bhp. These can be made to display any number to make the customer happy and might as well be like comparing different forms of currency; some are like USD/GBP/EUR, and others are like Zimbabwe dollars. What really counts is the % difference between the original and tuned runs.

Regarding peak torque at 4700 rpm vs 6200 rpm, I would more so question if a Z4M with high duration camshafts experienced torque falloff after 4700 rpm. The torque curve should be relatively consistent and flat in that range, which it is. I’ve tuned some cars that make slightly more torque in the mid-4000 rpm range, and others that continued to climb marginally higher like OP’s. FWIW at 4700 rpm, OP’s Z4M makes more torque than it did with stock cams.

Installing 100 cpsi cats on a Z4M running alpha-n requires a retune. Increasing airflow without a retune may throw the fueling out of calibration, which would result in less power. If the ECU has been properly tuned, 100 cpsi cats will only help power. They won’t cause a reduction at low rpm.

I have never been brought a Z4M that was fully optimized, and I have ALWAYS, 100% of the time found power. This is not a knock on anyone, it’s simply the fact of what I’ve encountered. Tuning these cars takes a huge amount of time, commitment, and knowledge of methodical approaches to reach peak performance. In many instances, critical aspects of the tune are unfortunately overlooked or misunderstood. At worst, the tuner may claim to know magic and that he doesn’t need to spend significant hours testing because he “knows these cars”. We started with a Z4M file I’d previously made that was based on a culmination of 50+ dyno runs of a very similar car and probably 95% perfect as-is, and it still took another 15 iterations to get this car dialed in to my satisfaction. We brought everything together with the final tune, and the result is a beautiful, linear power curve on a Z4M which makes the same or significantly more power than OEM at nearly every rpm with superior drivability.

Feel free to shoot any questions my way!

[buzyg]

Loved reading this thread. Some great comment from Pokey Britches at the end there.

[1536Z4]

Hi guys, Josh the “mapper” here.

Nice informative post Josh Looking forward to March and getting mine done .