stock gen 5 on dyno Hoonigan

[txA&M08]

So the calculator cannot be THAT off.

My bet is on a massive overestimation of the Viper's ponies. For the sake of marketing. Meanwhile, McLaren and Porsche are doing the opposite... they underestimate the wheel HPs on basically all their vehicles.

So basically we have here a Viper Gen 5 advertized for 640hp that loses almost 17% for an average of 533whp on a reliable dyno, but then in real world it performs as a 480whp.

Is it because it pulls timing like crazy?
Is upgrading to Motec the answer?

Weather conditions and how hard you are willing/able to shift are huge factors, as Steve pointed out. My car should be making around 570-590 whp, with just ARH catted exhaust, an underdrive pulley and an Arrow PCM. Yet with good air, it went 6.64 60-130. If you care to cross reference a bunch of cars that do 6.6 - 6.8 60-130 times, you could easily assume a 135mph trap, which is not bad at all for a 580 whp car.

[Aevus]

Weather conditions and how hard you are willing/able to shift are huge factors, as Steve pointed out. My car should be making around 570-590 whp, with just ARH catted exhaust, an underdrive pulley and an Arrow PCM. Yet with good air, it went 6.64 60-130. If you care to cross reference a bunch of cars that do 6.6 - 6.8 60-130 times, you could easily assume a 135mph trap, which is not bad at all for a 580 whp car.

not familiar with 60-130 times converted in whp (and not sure how reliable it is compared to trap speed) but a 580whp 3600lbs car should make 134mph, again based on the calculator.

yup, I think I'll head directly to a drag strip instead of losing my time with dynos (especially with my 4.10 gears..)

[Aevus]

Don't underestimate the effectiveness of a DCT when it comes to quarter mile times and traps.

I think it is also well known and well understood that the Gen 4 & 5 Vipers pull a significant amount of timing when things start getting warm. It only takes 77 degree F intake temps for the stock PCM to start pulling timing, and it does so in a hurry. I think the engineers underestimated the impact of said timing pull when it comes to power production, but that's the trade for engine longevity. I've seen stock-ish Gen 4s trap anywhere from 122-129 depending on weather conditions. Gen 5s don't pull timing quite as aggressively as the Gen 4s from what I've seen, but it's still there.

2-3 mph loss compared to DCT?


Gen 4-5 are the only one affected by timing pull?

[Old School]

2-3 mph loss compared to DCT?


Gen 4-5 are the only one affected by timing pull?

Gen3's start pulling timing at 122 IAT.

[Steve M]

2-3 mph loss compared to DCT?


Gen 4-5 are the only one affected by timing pull?

Depending on the quality of shifting (hand/foot speed and shift RPM point), I'd say 2-3 MPH easily.

And Gen 4/5 cars certainly aren't the only ones affected by timing pull, but it is extremely noticeable in both of those generations.

Stock, on a hot day (like 90 deg. F ambient) and after sitting at a traffic light, it literally felt like someone threw a boat anchor out. My car went from "holy shit, this thing is pretty fast" to "what the hell is wrong with my car?"

[SRT BILL]

Does anyone know when the Arrow controller for a gen 5 starts to pull timing?

[Sniper]

When does the stock pcm start pulling timing?
And would it be wise to raise the temp on pcm when it starts pulling timing with hp tuners with a 170° thermostat?

[Steve M]

Does anyone know when the Arrow controller for a gen 5 starts to pull timing?

Based on what people have reported, it likely happens at the same temp as stock.

When does the stock pcm start pulling timing?
And would it be wise to raise the temp on pcm when it starts pulling timing with hp tuners with a 170° thermostat?

Wise? Probably not. They tuned it that way for a reason, and it's likely a longevity thing.

Have I changed mine? Yes, but I'm assuming all risk. I have no warranty to speak of, and blowing my engine is always in the back of my mind. That will be a very sad, very expensive day.

[Sniper]

Steve, what did yours from and to?

[Steve M]

Steve, what did yours from and to?

That's a complicated answer.

At the drag strip, I don't let it pull any timing for any reason. What I command in the main spark table is what I get, but only for that application.

On the street, it starts pulling timing at an intake air temp (IAT) of 77 degrees F just like stock, but not quite as aggressively.

That's not the entire story, though. For both the Gen 4 and 5, the PCM pulls timing by a variable named manifold air temp (MAT). There's no temp sensor in the manifold (at least not that I'm aware of), so my guess is that there is a simple scaling factor that calculates MAT from IAT, but there may be more to it than that that would involve MAF and MAP readings. With HPTuners, you can set the tune to either pull timing by MAT or IAT - I chose the latter for simplicity (I can log IAT values, but not MAT).

The PCM will also start pulling timing for too high of engine coolant temps - for a Gen 4, anywhere over 185 degrees F ECT and it pulls timing (I'm not sure what it is for a Gen 5). For my street tune, I don't let it start pulling timing until the coolant gets to 203 degrees F, and again, not as aggressively as stock. Keep in mind that there's also a multiplier in play that scales by cylinder airflow - i.e., the multiplier that affects how much timing gets pulled for IAT and ECT is generally less than 1 for low airflow values, and goes up to 1 as engine airflow increases.

I also run more timing across the board, and I've eliminated the overly intrusive torque management that only seems to affect Gen 4s (torque management also pulls timing) - in some places, I'm getting about 6 degrees more timing than stock. On average, probably about 2-3 degrees of additional timing across the board, mostly in the WOT regions.

It gets messy in a hurry - there are a lot of interrelated variables that make blanket statements like "at 80 degrees, I know the PCM pulls X amount of timing" not entirely accurate.

I also have 0 durability testing to back up any of what I've done. All I can say is that my car hasn't blown up yet.

But it might.

[Jack B]

The Gen5 PCM does not really pull excessive timing until the IAT reaches 95F, after that point, the HP goes quickly south. The problem is, that temp can be reached very easy on the dyno. As an example, the IAT can routinely run 20 degrees higher than the ambient temp if the car is sitting or slowly moving. This is especially true if the airbox and tubes are not insulated.

[Steve M]

The Gen5 PCM does not really pull excessive timing until the IAT reaches 95F, after that point, the HP goes quickly south. The problem is, that temp can be reached very easy on the dyno. As an example, the IAT can routinely run 20 degrees higher than the ambient temp if the car is sitting or slowly moving. This is especially true if the airbox and tubes are not insulated.

One other thing I failed to mention is that it isn't just the timing being pulled that's the issue. Fuel also gets added at a rate proportional to the amount of timing pulled - the more timing that gets pulled, the richer the WOT air/fuel ratio goes as an added safety measure. This happens anytime timing gets pulled - for IAT/MAT, ECT, or knock. Even before you could monitor knock in the scanner, you could tell if there was knock by just looking at the commanded AFR. If it was knocking, the commanded AFR would go rich for a little blip and then back to normal once the knock went away.

At one point many years ago, I copied over the Gen 5 spark enrichment table values into my Gen 4 tune, logged the data, and graphed the results. The vertical (Y) axis is commanded AFR, the horizontal (X) axis is engine RPM, and the different colored lines represent different amounts of timing pulled:



I obviously have no idea how much power loss would be associated with each, but it all adds up.

My biggest issue was with torque management, though:



The blue line represents the amount of timing the PCM allowed with torque management enabled. The red line represents what I was commanding.

Needless to say, getting rid of that really woke my car up, especially under 4,000 RPMs. Again, that was pretty much just a Gen 4 thing - from what I gathered, it wasn't nearly as pronounced on the Gen 5s, if it was even there at all.

[Aevus]

Our running average for stock Gen V's is sitting at 533 WHP, and that's including the outliers like some low units registering 499, and one "freak" that made 557. These are 100% stock as baselines on the cars before we build them. Be sure to hone in on me saying there that STOCK Gen V's have varied as much as fifty-eight rear wheel HP, or nearly 10% in other words. This isn't that uncommon in the realm of OEM cars when you look at tolerance stacking of internal parts which can change static compression ratio for instance, then build tolerances for leakdown, then sealing tolerances for used engines over time.

We've tested a LOT of different combinations, including Prefix Head/Cam cars, 9.0L standards, 9.0L X's, other aftermarket companies head/cam cars, etc. To date we've never seen a stock displacement Gen V make over 700 WHP NA on our dyno even though there are plenty of claims out there that it's "normal". The Prefix stuff is very consistent, with the standard displacement head/cam cars usually making right around 635 - 655 WHP, which is a respectable 120 WHP gain on an already rather powerful (OEM) NA engine.

This is all SAE corrected above, but note that chassis dyno's are not held to a singular method for measuring/deriving power across manufacturers. That means that each MFG has their own way of deriving the power figure based on the input information available, and even the MFG's that use the same style of load sensing can choose to calculate those values differently.

Take all the above for whatever it's worth to you, but I assure you that you'll just confuse and mislead yourself trying to draw comparisons from one dyno to another, with different cars, in different climates, etc. There just isn't an accurate enough way to do it, unfortunately. Even basing things off of 1/4 trap speed, something we as a company are very familiar with and usually basing judgment from - is so highly impacted by Density Altitude that it can surely skew your comparison if you're not aware of it.

For us, the true measuring stick is an A to B delta on your car, your engine, same dyno, similar testing method and weather if possible. That's as close as you can get to factual information on the change provided by a set of modifications.

So I can kiss goodbye any hope to ever make 700whp N/A with my 8.3l engine, E40 or not, Ti valves or not and shaft mount aluminum rockers or not?

[Aevus]

We've built NA stuff that has stock displacement and made over 700 WHP (740 actually), but it was a built engine, MoTeC, really good valvetrain, ethanol, raised compression, a lot of cam (which was only drivable due to having a MoTeC) etc.

Just noticed that reply, thanks that's interesting.

So stock displacement N/A, absolute maximum is +/- 740 whp, while moderate ''Prefix-like'' kit is around 640-650whp or so...

[13COBRA]

Just noticed that reply, thanks that's interesting.

So stock displacement N/A, absolute maximum is +/- 740 whp, while moderate ''Prefix-like'' kit is around 640-650whp or so...

Which is what I saw on my car. It put down 641/639.