QOTW #52 – Aftermarket Exhaust Manifold and Cat Comparison

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Welcome to Bamford Rose and another question of the week. This week, I’m going to talk about aftermarket V8 Vantage exhaust manifolds. This is a question that I’ve seen lots of times. It often goes along the lines of someone right on a forum saying, ‘Hey, well there’s a few different places that you can buy these. Are they all the same? Do they all do the same thing?’ And then depending on the place that this subject is being spoken about, maybe there’s some vendors of each system that comes on. And maybe there’s some customers, there’s some informed ones and there are ill informed ones, making statements from no particular piece of data.

So, I only put my thoughts to it. Take them and leave up to you. First thing is, there’s probably three places you can buy exhaust manifolds for a V8 from. Where one vendor, there’s a company called Top Gear. That’s another one and there’s a company called Velocity. So, on each one of the three, I think we’re the only ones where you can find actual tangible real photos of where they’re made, okay. So, here’s our fabrication shop. Obviously, if you’ve been on a lot of our social media or our website, then you’re used to seeing what a fab shop looks like. And you know that they’re made on site. Made in the UK, made by us, fit by us. Quality control, fitment, absolutely everything. Performance, sign-off, absolutely everything all under one roof.

For the other two vendors, I have never ever seen a tangible picture of whether you’ve been making a V8 manifold. That’s because I should imagine it’s somewhere in Eastern Europe somewhere. The next is the manifolds themselves. So, people are saying right, ‘Well, are the performance results the same?’ And some people pop up and say, ‘Well, you know they’re not made with the right collector order or the primary pipe diameter secondary pipe diameters are a bit small.’ And people that make that comment yeah, it’s true. But I’ve never seen a properly designed VA exhaust manifold from any vendor.

We’ve seen them here because we often get the cars delivered here when the customer has fit the upgrade and the performance doesn’t meet their expectation. In those cases, we take off the other half the market kit put ours on and the customer is Wowed. So, we’ll go through the reasons why now, and just flash up a few pictures of our exhaust manifold. We make them in any style, for some motorsport applications, we’ve used merged collectors. I have not really seen the difference in performance between a merged collector and a press collector. It’s a very small distance and if the volume is big enough anyway that whatever collector is not playing too much of a crucial role in terms of aiding performance.

It’s just that the merge collector is more mobile and that’s what the motorsport world uses, because it buys this collector that’s already formed. Whereas actually if you can make the collector yourself, I can get it for a cheaper price and it does the same job. So, anyone saying, oh well that’s a merge collector versus a press collector, there’s no real difference in it. We’ve made the exhaust manifolds in the configuration of firing order to aid scavenging. We’ve also made it, so it’s not and again on the dynos tin absolutely no difference really whatsoever in intangible measurable performance.

So, I don’t rate the design of the collector either merged or pressed or the configuration of the primary pipes into the collector in firing order. I don’t really rate any of those as significant. What is significant is, the length of the primary pipe and internal diameter, therefore the volume of gas stir that can hold before it expels the gas pushes the gas into the collector. And obviously, the collector volume is important and the secondary pipe length diameter. Therefore, volume is important too. So, what we can do now is flash up some pictures of our manifolds side by side with someone else’s. First picture has them both on the table. And immediately you can see from that picture ours is in the foreground, the other one is in the background.

You can see that we maintain an absolutely perfect centerline radius going through every single bend. Now if you look at the primary pipe what’s it going to be cylinder 5, this is going to be the primary pipe in the top left-hand corner of your picture. And the primary pipe on the manifold in the background for cylinder 8 and you’re going to see that that centerline radius as it goes through those bends is not truly inconsistent. This means that instead of the entire internal diameter of the pipe nicely flowing gas, it’s going to be somewhat closed shutoff. Because the bend is not following a consistent centerline.

Next thing, we can look at a picture of the collector. I mean this clearly a choke point of the primary pipe going into the collector on that particular system versus what you can see on our pipe. Which is a nice consistent diameter going through the whole collector. We now put Vernier on our primary pipe and we measure there 43.6 mil outside diameter and on the other one 41.37 outside diameter. Now the pipe used with the grade of steel that is wise to use, means about 1.5-millimeter-thick this pipe. So, by the time you take that away from your 41 that they’ve used, that super super small primary length.

So, that’s why performance on that manifold feels choked at the top-end compared to ours. It’s because as the engine is revving through 5, 6 7, 7 & half thousand RPM certainly when it gets to 665 is choked. Because that diameter is too small. Next is we get these nasty looking instruments out. And measure the neck, the opening of the primary pipe from the flange and we record a 38.13 on the other set of manifolds. And you can see the picture we’ve done the same on ours, and now we are 41. So, our internal pipe diameter is larger than their external pipe diameter. Significant measurements are in terms of affecting how the engine is going to breathe.

Next, we come on to the actual detail of the entry into the primary pipe. And you know there’s pretty nasty welding going on the inside there. So, it’s small diameter and it’s interrupted by an unsmooth surface. Where you can see the shot of ours now you know the welding on the inside is as neat as the welding on the outside. This is because it’s been properly purged and welded. And if it’s been not properly purged welded, it’s going to be susceptible to cracking due to contamination a weld at the point of manufacture. So, not only is this a not the best performance it could be, it’s also compromising the longevity of the part.

Next picture we flash up here, this is the internal detail of our collector. And we’ve got a nozzle which sort of acts to accelerate gas speed as it’s coming out which in turn scavenges out the next gas in turn. We’ve got there are really big nozzle on ours. And you can see from the picture of the other set that in comparison, it’s not a nozzle at all. I don’t know what that’s doing, so you’re not going to aid the speed of gas flow and promote a scavenging effect.

A couple of pictures now just on different angles in the manifold. You can see ours; we maintain really nice consistent centerline radius. And you can see there on this picture of the other manifold that as the primary pipe immediately comes out the flange that first bend there’s pretty nasty. Then there’s that long straight section. And again, as that sweeps under the other pipes there is not maintaining a consistent centerline radius. So, the internal diameter is being closed off and made less, because of an inconsistent centerline radius from a primary pipe which was already a smaller diameter.

Next, the catalysts. I’d have to set the fabricator if these are ours that’s pretty atrocious welding. It’s not gonna fail, it just doesn’t look too nice it doesn’t look symmetric. You can see there that as the cone comes out into the exit pipe, it’s not symmetrical. And the big one here final shot, you can see the diameter of their catalyst so just have to zoom in myself. The Vernier there is set at the diameter of our catalyst, which is 107 millimeters. You can visually see how big our catalyst is compared to that one. Again, combined with the small primary pipe diameter, this is going to significantly affect gas flow.

I’ve driven all of these cars that came here myself, had this kit taken off and asked put on. When you get to 6,000 RPM with our kit it’s not like a two-stroke motor bike, it’s nowhere near it. But it’s as if the engine is coming into a second breath of air and you almost get that two strokes or power band of air. When I drive these cars, it’s strangulated. The engine is not free revving up to the redline and as opposed to standard car, take that for a run down the road. There really is no performance difference. So, you know there’s lots of people there that say well, you know a manifold is a manifold and it gets rid of the catalyst. They’re all of similar design, it makes no difference which one you have. Beg to differ, attention is in detail.

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