Frankenstein’s Unicorn
DISCLAIMER
The information provided here is for general guidance purposes only. It is a combination of manufacturer guidance, first- and second-hand experience, and personal opinion. It may me inaccurate, incomplete, or outdated.
Saying I’ve had lots of projects in the works lately would imply that I haven’t been losing my goddamn mind trying to manage everything going on. I don’t mean just projects with my car, or product development, or running Redpants - that’s all enough to run me ragged as-is. But no, it wasn’t just that. During all the above, I was also in the process of getting married (by proxy) and moving to Japan (during a pandemic), neither of which was easy on their own, let alone together, let alone alone while handling everything I do on a daily basis for Redpants, let alone alone alone while overhauling my supercharged 2007 V8 Vantage. The last couple weeks alone were so absurd that it warranted a mini-update by way of a Blog post.
I don't know how to explain how hectic the last several months have been, but trust me I'm trying (I have a few Articles and videos for Redpants and a huge workload piled up for Redpants Unzipped). This particular Article is about one of the many things that has been going on but it might seem a bit abrupt since so many things happened all at once. It’s about my new engine.
Some time a go my buddy Alistair over at Valiant-Ecosse in Germany offered to sell me an engine he had sitting on the shelf. He had a bunch of projects and the lump of metal was just taking up space and collecting dust, so he said he'd give me a killer deal on it. I wasn't in the market for an engine until he explained what it was - it was one of the original N24 engines built for Aston Martin Racing. There were fifteen Vantage N24 race cars (including the prototype "Rose") originally built. One of those cars would later have the engine replaced by the 4.7L GT4 engine when that became available, and its original engine would eventually make its way into Ali's hands. Not only would I be getting that engine, but the original builder - the legendary Bruce Bermingham - would be rebuilding it to even higher specifications. And, Ali was right, the price was a hell of a deal. How could I say no?
But that wasn't all we'd be doing with the engine. After Bruce had finished the engine, Graham hopped over from GMR and supercharged the engine to create an absolute monster of a powerplant - one that could rev to the moon and back while also providing waves of torque at any RPM with a squeeze of the throttle.
Between its history and rebuild, plus the addition of some VelocityAP and Redpants parts, it became a Frankenstein's Unicorn.
A Bit About the Engine
The best way to summarize this engine is that it puts out a huge amount of power over an incredibly wide rev range by combining the low-end grunt of a supercharger with the high-revving capacity of a race engine.
I often describe the standard 4.3L as the rotary engine of the V8 world - it sings beautifully and puts out decent power above 4k RPM, but it's gutless in the lower half of the rev range. Things like an engine tune and a twin-plate clutch and lightweight flywheel can help quite a bit, but the engine still does far better in the top half of the rev range. A supercharger fixes that by providing a huge increase in torque, especially down low.
Superchargers are sized according to the displacement of the engine and the intended use case for the blower. GMR actually use one that's oversized for Aston Martin's V8 engines but is done so with the latter consideration in mind - the larger compressor allows it to continue providing boost at high revs, where these engines enjoy being, while keeping heat generation lower than would be possible with a smaller unit. The end result is a package that produces substantial torque at low RPMs but can rev and build power all the way to the engine's redline and with less concern about heat generation which mitigates the lack of intercooling.
In real-world scenarios, that means less shifting and more casual driving in city traffic, and being able to leave the transmission in 6th gear when passing on the highway. At Lime Rock I was able to leave the car in 4th gear for most of the track, only needing to shift into fifth on the main straight. Staying in one gear allowed me to focus far more on steering with both my hands and my mind.
Maximum boost pressure is about 8.5 PSI. It's important to note that this is the maximum boost pressure the engine will see and it’s generally rare to actually see it - the vast majority of the time, the intake will be either under vacuum (as with a naturally-aspirated engine) or at a lower boost pressure. It's only under full load and high RPMs that boost will hit its maximum pressure. In normal driving, the supercharged engine is counterintuitively less-stressed than it is with the factory naturally-aspirated design. The reason is that it takes much less effort for the engine to produce more power, especially in the low-to-mid RPM range where the supercharger provides a massive increase in torque.
At peak boost, GMR say the engine experiences only about a 10% increase in cylinder pressures. Meanwhile, strain on the reciprocating engine internals (the rods, pistons, bolts, etc) see a drastic increase in force as revs climb, with RPMs being squared as part of the calculation. Here’s how that looks when plotted out.
Caveats and additional info about this graph:
The chart shows simplified data using the same calculations, measurements, values, etc, as described in this article. The intersection and terminus points of the RPM and Inertial Load lines are entirely arbitrary. I overlaid them the way I did to show that a steady/linear increase in engine RPMs (the blue line) equates to an exponential increase in inertial load of the engine’s internal components (the orange line). This chart is meant only to show the relationship between RPMs and Inertial Load, not actual values.
The engine needs to be revved up regardless of whether it is naturally aspirated or has forced induction if you want to get more power so you can accelerate, even in normal driving. A small increase in RPMs and low boost pressure with a supercharger exert far less strain on the engine than revving a naturally-aspirated engine up to far higher RPM levels for the same (or less!) power increase.
An added bonus, albeit one that doesn't rate highly for most of us, is that there's also a considerable increase in fuel economy. Yes, flogging an engine with forced induction will likewise negate any fuel economy benefits. You'll see the same low-single-digit MPGs at full throttle whether you've got a supercharged engine or not. But in normal and even spirited driving you'll get better fuel economy. For example, I was getting 28 MPG at 80 MPH while driving cross-country and was seeing low-30 MPGs at lower highway speeds. Given 2022's fuel prices [political commentary deleted], the supercharger might eventually pay for itself! In a more practical sense, it meant my road trip required fewer stops for fuel - I often stopped to stretch my legs and empty my bladder well before I actually needed to refill my gas tank.
A key design aspect that people need to consider if they want a GMR supercharger kit is whether to get the non-cooled option or the one cooled by water injection (which I’ve termed as the "Dry" or "Wet" option, respectively). The latter includes a water injection system that cools the intake charge and helps clean the engine’s valves. The cooling factor is the important part (the steam-cleaning is a nice added bonus) and is what the vast majority of customers want when they talk to me about these kits. The issue, however, is that the water injection system adds substantially to the price. The Dry kit doesn’t include any active cooling measures.
I opted for the dry kit to [theoretically] make it easier to get my car registered in Japan, while also wanting to test the kit to see if concerns about the lack of cooling are justified to the extent people seem to have. My trip across the US and participation at the AMOC events (particularly the track day) would push the setup more than just about anyone else ever would, so it'd be a good test to see how much of an issue the non-intercooled and non-watercooled supercharger would have.
A quick recap of the real-world testing: I ended up driving about 3000 miles in eight days. First was the drive from Idaho to New Jersey, starting on Sunday evening and getting to Newark on Wednesday evening, where I picked up my wife from the airport when she flew in from Japan, then we drove straight away to Lenox, MA. The day after arriving in Lenox was the track day at Lime Rock. The next couple days included a small bit of driving but following the event I drove back to New York City on Monday and then to my buddy's house in New Jersey the next morning where I dropped off my car to be shipped back to Idaho while Luanna and I flew back to Japan from Newark.
Having the supercharger on the long highway drives made the trip much easier as it took so little effort to overtake other vehicles, even large trucks in tighter spaces. The greatly-improved fuel economy meant I could worry less about finding fuel, especially out west where gas stations could be few and far between in some areas. Essentially, it made the journey much more relaxed, although it did make Nebraska a bit more boring. Where it really shined was during the track day, though. The supercharged N24 engine was an absolute beast on Lime Rock with more than enough power to send the car flying around the track without needing to downshift at all other than dropping back down to 4th gear after running up to 5th on the main straight.
There were no issues with heat during the highway cruising or track day. At the end of the 12-hour days driving cross-country, the car (and engine) seemed a bit weary... or maybe that was just me. I was generally keeping the engine at about 4000 RPMs all day long and that would tax any engine, so I can't really hold anything against this one as it seemed to me that both myself and the car felt the same as the naturally aspirated setup had been in my previous cross-country journey.
The only issues I had were dealing with heavy traffic in Manhattan, which would have been just as much of a nightmare regardless of whether or not the engine was supercharged - really the main issue there was driving a low-slung sports car with a manual transmission in that hellish traffic and on those rough roads.
GMR advertises their Dry supercharger kit as producing 550 BHP, but a bone-stock 4.3L V8 with the same supercharger kit was dyno'd at 570 BHP. Mine isn't bone-stock, and you can check my Build Page for a complete list of modifications. The key ones are the engine itself, the headers, clutch and flywheel, and intake which has Redpants Air Box Deletes and Redpants Intake Filters. If a bog-standard 4.3L V8 puts out 570 BHP, I'd say mine should put out around 600 BHP. The guesstimated power increase doesn’t tell the full story as my engine is also more responsive due to the lighter and stronger internals. I wanted to explain that for the sake of full disclosure since I do sell the GMR Supercharger Kits and don't want people to think I'm misrepresenting anything - this article is about what's in my own car. If you're considering supercharging your car, you'll notice that power increase far more than the differences that I've got on top.
And It Keeps Going…
As over-the-top as my engine is, it’s actually something of a half-way point during a longer-term project. My bigger goal is to have my original engine rebuilt into a 4.5L low-compression setup that’s built for bigger boost with the goal of hitting 700 bhp. The joke I often tell when discussing the goal is that having 700 bhp will read out as “007” when I lose control of the car and slide out backwards.
I hope that’s not a self-fulfilling prophecy.
It’ll be hard to commit to the yet-bigger build because what I’ve got is already so damned good. It’s already cost me a small fortune and doing it again with a second engine… well… ouch. Y’all can help make it happen if you’re feeling drunk or generous enough lol. I’m also really in love with my car’s current setup and there’s very little I’d want to change. So, I might end up looking at getting another Aston Martin, yet again, to explore a stupidly wild build.
That’s not to say development with my car is done - far from it. I have a couple projects in the works, one fairly far along, that I’m hoping to turn into production items soon. I’ll be bringing my car to Japan later this year and will continue working with it to bring you guys more products, DIY Guides, videos, and everything else that I can. But that’s a bunch of stuff that’ll happen as it happens. Until then, I’m absolutely flabbergasted (yes, flabbergasted) by this engine. It’s seriously good.
Of course I do have a vested interest in selling these supercharger kits, and they are available in my Online Store, but I wouldn’t sell something I don’t believe in or wouldn’t use myself. By going all-in on not only a race engine but also supercharging it, and then putting it through 3000 miles and a track day immediately after installing the thing, I hope it shows that the products are sound and worthwhile if you really want to push your Aston Martin V8 Vantage to its limits and beyond.