When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Whoa, is there a new tune for the X51!? Since I switched to the GT3 center exhaust I've been thinking it might be worth seeing if the dyno shows any new hp and/or if it's worth seeing if optimizing the tune for the new exhaust. It sure sounds faster and flames at night are cool....
I will have to look. I do actually...but there's no sound! There are however flames!!!!!!!!!!!!!! I spent some time with the Cobb guys here this winter/spring tinkering with their "pops and crackles" maps and the one we tried was so aggressive that when i was driving by a farm it made the livestock scurry!
Hey buddy...I was able to get Cobb to give me some access to some tables that allowed me to make something more tailored for the X51. It involves moving some wires around and hooking up a thing or two. I told Rick I would walk him through what to do so you should make an appointment with him to get the update. This was something I waited on for a while with Cobb and they delivered, as they always do.
hell, i want to see the Stage 1 - 3 quote now too. you guys are like crack dealers
Nah, a crack dealer would give the first trial for free; I had to charge you for Stage 1. It's when you come back for more that I sharpen my pencil and find a way to discount the product!
Nah, a crack dealer would give the first trial for free; I had to charge you for Stage 1. It's when you come back for more that I sharpen my pencil and find a way to discount the product!
ha, if you guys remember, i was the guy who forgot his checkbook and had to count out bills onto Wray's desk. just like a drug deal!
I realize it's been a while since i have added anything to this thread so i figured i would update it with this morning's dyno run; this graph illustrates the addition of a revised TPC GT3 style exhaust for the GT4, CNC ported cylinder heads that we are doing on all of our Stage II and III conversions and our new bore increase to make it a 4.25L!
The increase in the bore from 4.0L to 4.25L created a big bump in the amount of torque and horsepower down low. Since i am able to get that power sooner, i am not revving the snot out of it in an attempt to be as conservative as possible. With the ligther bits from the GT3 and a different intake setup, we could reconfigure it to make more power up top but we can't spin it that high because of the ECU architecture. For comparison purposes, here is that dyno run vs. a stock 991.1 GT3.
It's always so hard to make sense of wheel power numbers like this. A 991.1 GT3 makes 475ps stock. And Porsches pretty much nail their claimed crank power on a MAHA dyno every time.
So now with all those goodies like X51, ported heads, a race exhaust system and 0.45 litres extra displacement the former 3.8 is finally more or less matching the old stock 475 crank GT3 which does that with a stock emissions compliant exhaust...and at nearly 1500rpm higher with possibly bigger tires so certainly no less drivetrain/friction loss than the 981. So it would be difficult to use logic and conclude that the 981 is making more than 475 at the crank.
Puts some vendors claiming 450 or more crank power (using creative loss percentages) with simple bolt ons and a tune in a not very realistic light I'd say.
It's always so hard to make sense of wheel power numbers like this. A 991.1 GT3 makes 475ps stock. And Porsches pretty much nail their claimed crank power on a MAHA dyno every time.
So now with all those goodies like X51, ported heads, a race exhaust system and 0.45 litres extra displacement the former 3.8 is finally more or less matching the old stock 475 crank GT3 which does that with a stock emissions compliant exhaust...and at nearly 1500rpm higher with possibly bigger tires so certainly no less drivetrain/friction loss than the 981. So it would be difficult to use logic and conclude that the 981 is making more than 475 at the crank.
Puts some vendors claiming 450 or more crank power (using creative loss percentages) with simple bolt ons and a tune in a not very realistic light I'd say.
Great stuff though BGB, love it!
That's the thing; it's not totally apples to apples because the .1 GT3 with a free flowing race exhaust manifold and tuning would be stronger. This is basically a fully modified car vs. a stock GT3. HOWEVER, your point about claimed bolt-on power numbers from other vendors being overly aggressive is something with which i struggle constantly. I am very conservative and harsh with my numbers. I like the thing to be heat soaked and i like to see the worst possible scenario because i want my customers pleasantly surpised and not disapointed when they do their own dyno analysis. The MAHA dyno is rather awesome. I do however trust the wheel numbers of the Dynojet as it's one of the most repeatable dynos around. I think that the wheel power numbers would impy that the GT3 is making over 500 crank, which we know it's not supposed to do but i trust the repeatability of it all.
It's always so hard to make sense of wheel power numbers like this. A 991.1 GT3 makes 475ps stock. And Porsches pretty much nail their claimed crank power on a MAHA dyno every time.
So now with all those goodies like X51, ported heads, a race exhaust system and 0.45 litres extra displacement the former 3.8 is finally more or less matching the old stock 475 crank GT3 which does that with a stock emissions compliant exhaust...and at nearly 1500rpm higher with possibly bigger tires so certainly no less drivetrain/friction loss than the 981. So it would be difficult to use logic and conclude that the 981 is making more than 475 at the crank.
Puts some vendors claiming 450 or more crank power (using creative loss percentages) with simple bolt ons and a tune in a not very realistic light I'd say.
Great stuff though BGB, love it!
It's pretty crazy and yeah, dynos are all over the place so whp number alone can be relatively directional but not absolute. Comparing against similar dynos (e.g. dynojet to dynojet or dynapack to dynapack) I think helps since those numbers seem relatively close but there are still a lot of environmental variables. You really can only go with the before after dynos and the rwhp difference on the same dyno which is why it's cool when BGB releases these.
Also agreed that a lot of the bolt on HP claims are a little bs BUT at the same time, I've been really impressed with how much power bolt-ons can make even if not quite matching the claims from the vendors. For an NA engine there really are a lot of gains to be had since Porsche detuned the engine so much stock - I think of the stock 991.1 GTS 3.8 @ 430hp as the measure of how much potential is in the 3.8 before opening the engine or losing the cats.
Having also seen and driven modded 3.8L, 4L, 4.25L, 4.5L GT4s and 991.2 GT3 manual (PDK is a whole different ballpark) I'm a believer, there are definitely GT4's making the dyno numbers and feel like more than 475 crank hp. One thing that's worth nothing in BGB's dyno is the low/mid range torque. Gearing aside (which is sooooooo long in the GT4) trading an extra 1k rpm on the top end for more immediate torque in the low/mid range does make for a very different driving experience between a 500hp GT4 and a 500hp GT3.
Having also seen and driven modded 3.8L, 4L, 4.25L, 4.5L GT4s and 991.2 GT3 manual (PDK is a whole different ballpark) I'm a believer, there are definitely GT4's making the dyno numbers and feel like more than 475 crank hp. One thing that's worth nothing in BGB's dyno is the low/mid range torque. Gearing aside (which is sooooooo long in the GT4) trading an extra 1k rpm on the top end for more immediate torque in the low/mid range does make for a very different driving experience between a 500hp GT4 and a 500hp GT3.
Definitely good gains to be had with simple mods, and they arguably make the car feel like it "should have" from the factory. You rarely see good direct comparisons like the one posted by BGB here, which put the numbers in a decent context. Wheel numbers are still tricky obviously because changing pressures, tires or wheels makes a real difference and so does gearing. But it gives a good hint of engine power when one is a known quantity like the GT3 here.
The sensation of acceleration is a funny thing. I've not driven a Touring but I did drive a Speedster (a lot harder than the police in Sardinia would have appreciated too) and I thought it felt fast. The shove in the back after 6K or so was pretty impressive. My own 981 GTS PDK on the other hand I've just swapped a 3.8 X51 into which was then given the Ehresmann treatment, and even though I've picked up something like 80 HP peak and 100++ nearer to 8000 RPM it only feels slightly quicker than before. Especially in 3rd-4th-5th it's almost hard to tell. But use a stopwatch and the difference is staggering. The shape of the torque curve can really hide how quick a car is perception wise. Along the same lines you can make a car feel quicker too with lots of torque early on.
A highly modified MA103(S) engine like this one by BGB is clearly matching the stock .1 GT3 just with the power curve shifted to lower RPMs due to the fundamental difference in the hardware. It could (should) feel faster due to the stronger low end.
08-21-2018 | 12:30 PM
and flames at night are cool....
