Carburetor Vs Direct Injection Dyno Test

本站添加: 2026-05-06

[00:00:00]Hey guys, this is Eric Wardner with Wuner Racing. I was wrong, completely wrong. I learned something new yesterday and it has made me think, rethink a bunch of stuff, but I was completely wrong. I will say if you watched last Tuesday's video, this will almost be an add-on to that one because there's something else that kind of gives it away that what I was saying you last week was correct, but what I was knew about this situation, I was completely wrong. What was that? I thought that carburetors would make more power than DI. DI stands for direct injection. And I'll give a generic example in this. But here's what happened. So yesterday I got to go to Kunen Company, which is in Archadadelphia, Arkansas, and I got to work with Brad and Aaron. They work for Counen Company and GPI. GPI and Co are kind of together. They're like one company essentially. And anyway, they have a new dino cell that they set up there. And they set up an LT engine to let me use to do this test. and they were gracious enough to allow me to test whatever I wanted on it. So, we got to test a few different things. So, before I get into that, let's talk about what actually direct injection is and you'll see why I thought this isn't this shouldn't beat a carburetor. I mean, that's my old school thought. Now, I know that to be false and wrong, but let's talk about what a DI is. So, um DI stands for direct injection. If you're an old school guy, the very first fuel injectors actually look more like a um throttle body, almost like a carburetor, and they'd spray pretty much where the interior was. They'd spray have an injector, and then they'd spray down. Later models, then they use something called uh port injection. So, they have an injector about here, and then they'd spray into the intake port, and then as the valve opens, the fuel goes in. Then, this is the latest iteration. And this is called a direct port head because this spot right here is actually where a direct injector injection in injector would go. This right here is a spark plug. This is an injector, but it sprays directly into the combustion chamber, not into the intake runner. So, the idea being behind it is fuel takes up space. So if whether it be a carburetor or a fuel injector up here, either one of those are taking up space in that intake runner. So if that's fuel taking up space, that air could be. So if you direct directly inject the fuel into the chamber, everything that goes through this intake runner is nothing but air. I can make the port smaller. You could essentially because I wouldn't need it to make as big, but oddly enough, they're bigger, which we'll get to in a minute. But anyway, the idea is more air goes through, you make more power. There's another benefit too that's also gets recommended as well is the thought that is you have a certain combustion or volume in here into this combustion chamber as it is once I inject the fuel it's automatically raising your in compression ratio because that volume of fuel is compressing everything else that's in there and essentially raising your com combustion ratio but anyway as far as I thought and remember this is not an engineering YouTube channel so if you're going there for that, here for this, you're in the wrong spot. But I had always thought that the carburetor and even poor injection to some extent should have the advantage over direct injection because to my mind, which there are some scientific principles to this, the carburetor, it in induces the fuel right at the very beginning of the intake charge. As fuel liquid turns into a gas, it takes out heat from the air.

[00:03:30]That's called latent heat of evaporation. So, by having the fuel at the top part of the intake runner, as it evaporates and turns into a gas, it's taking heat out of the intake charge, making the intake charge cooler and denser. We know that cooler and denser intake charges make more power. That couldn't have happened in a direct injection deal because it's injecting the fuel here, which to my thought was the cooler denser charge will make more power in this configuration.

[00:03:59]I was wrong. So now we could talk about the combo.

[00:04:04]This test would be very difficult to to do on a nondirect injection head. So before someone says, um, this is a great idea and all, but you used a direct injection head to test a carburetor, what you should have done is also try doing a carburetor head, one that's made for carburetors or fuel injection, and then try adding direct injection. That's extremely difficult to do. It's much more easy to do what we did. So, we use a direct injection head, this LT head, and we ran a carburetor on it. So, here's the combination. This is an LT engine. This is a 6.2 L. Kunen company did some work to it. I'll be quite honest with you, I am shocked. So, it's a stock block, stock rod, stock crank, stock pistons, stock rings. The only thing that they really changed on the bottom end was new bearings. They also did fly cut the pistons, so that is a little bit different, but they're still stock pistons. The rings were the same ones that they had on there to begin with. It got all slapped back together.

[00:05:05]Then they installed one of their cam shafts. I'm putting up the specs here because I don't remember what they are.

[00:05:10]This any one of you guys can buy it. And I'm not trying to be a salesman. I'm just giving you the information. Then they took the heads, the stock heads, and they ran their CNC program through them. This is the part that's going to shock you.

[00:05:24]The intake, this is stock, this is not their head, but the intake ports that were used for this test were 320ccc's on a 376 cubic inch engine.

[00:05:38]That's correct. You heard that right.

[00:05:41]That's like big block volumes. So, you're like, "Well, it's not the same.

[00:05:45]You see the runner link's longer with the LT." You're right. It's still shorter than the big block runner and it's as big. That's huge. So besides being bigger, um it's bigger than what you would normally I would ever pick to go on something of that size ever. But that's the head that they have on it.

[00:06:06]And you cannot argue with success. So I know eventually some of you are going to say, "Well, if the head maybe the head's too small and it couldn't work with the additional fuel that you put in it."

[00:06:14]That port's gigantic. There's no way that I wouldn't think that the fuel going through that port wouldn't work, but anyway, that's their ported heads. I don't know exactly what they they flow.

[00:06:24]I you should be seeing on this page um a picture of their GPI stuff in case you wanted to order it. And that's what they had used. We started off by just doing their basic thing because they wanted to test a few different things too. And they used just used a Holly Hyram and a front-facing throttle body. And they did some dyno tests and it looked like this.

[00:06:58]Yeah, it sounds clean.

[00:07:01]>> It's not.

[00:07:06]>> They were running stock rockers at the time. They had some mantins and mant those are smart design. I don't know how much they are. It looks like they're expensive. Anything Matt I feel like is expensive. But nice pieces because these rockers are different and and I don't want to I'll save that for them because I don't want to know if GPI is going to make a video with that or Matt is. But that rocker design, I really really liked it. And then they put those on. It wasn't worth any more power, but they just want to see if it would contribute to valve flow because there is a difference in the mass of the tip of the rocker with the Manton versus the stock one. It didn't have any effect. So, nothing at all. Then we began with what I was going to do. Obviously, we can't test the forward- facing uh throttle body with the with the Holly Hyram against the carburetor because we'd have to put on an intake manifold that could run a carburetor. And although Holly does make a dual um carb intake top for that, or throttle body if you want to run that, we didn't have one. So, what we did is they had one of these and they are extremely rare evidently. This is a CID single plane intake manifold for an LT. That's what makes it rare. They make them plenty of for the LS, but not so much for the LT platform. I think he said this is only the second one in existence. Maybe there's more now, but that's what they were saying. Very, very expensive manifold, too, from what I'd heard.

[00:08:26]Anyway, that worked perfect for what we're going to do because here's how we did it. So, the first thing we did is we ran it like this.

[00:08:56]If you notice, all we did is we took the carburetor. This is the carburetor we used initially. This is a Holly Dominator. David Viser had sent me this just to do some testing. So, I didn't figure he'd mind. But this is one of the Ultra Dominator, their XP kind of line, but it's got something that allows us to do it on this side right here. You'll see there's a spot, a provision for you to put a throttle position sensor because when you're doing the LT testing, initially what we were doing was doing drive by wire. Well, you can't do that with the throttle position or the carburetor, obviously. So, throttle position sensor and then this. And you might be saying, well, how did you get get your map though? Don't you need the manifold air pressure? You're right. So, what we did is we used a space underneath there, drilled and tapped a hole, and then because we're running the Terminator X um software and computer, we just did a vacuum line right to its port there because it's got a one bar map on there. And then we could run it.

[00:09:47]And that's what we did. So, we ran it just this using the carburetor is essentially the throttle body. No fuel being ran to it. And make our first dyno pools. And they sounded like this.

[00:10:09]As you can tell, they are wicked awesome sounding cuz we're going from like 3500 to 7500, but really you got to go to 7,800 so that records all the numbers.

[00:10:20]So, this dude is screaming. Um, it does have titanium intake valves on that on this particular engine. And I don't know if that's how they came from the factory, but this these ones do have titanium intake valves, but that's a lot of RPM for a Johnson, by the way, Johnson hydraulic roller lifters. Crazy amount of RPM to me. And it's making 730 something horsepower or whatever. So, really, really good. Um, I'll be honest, I was quite shocked. I I have really underestimated the LT platform by a far um a lot. And by the way, these are stock injectors. I know someone's going to ask. These are stock injectors that are running in run on it. I want to say they're running 2200 lb of fuel pressure. You might ask Aaron at GPI or ask some of the GPI guys about that. Um but anyway, it's all using Holly software, too. That's where why we're able to do it. I know some of you might be saying, "We're using HP software."

[00:11:17]No, because I I don't think it'd work very well with this situation. what we're trying to do. So, it was used on Holly. So, anyway, really good power.

[00:11:25]Before I put the fuel to the carburetor, I wanted to test one other thing just to kind of see. So, what I had decided and asked them, and they're really kind to let me do this. I said, while we still got this on there, I brought these ice bags and they're from Cool Ken's Cool Racing products. And what they are is there are these um there's special gel that's in this bag and you let it sit in water and it absorbs water. You put them in a refrigerator or freezer. You don't leave them in the freezer till they're frozen, but you get them really cold.

[00:11:54]And then you put them over the intake manifold and you let them sit there for like 10 minutes. You can even if you strap them down, you probably can make a run with them as long as they're not dripping water. Obviously, for safety hazards for a dyno, it doesn't matter.

[00:12:05]But we let it sit on there for about 10 minutes and then we made a pool because the idea with that is I want to see if the cooler charge would increase the power with direct injection because we're still direct injection. All I'm doing is cooling the intake charge to see if it makes any more power with the direct injection because essentially that's what the carburetor will be doing with the fuel is cooling the intake charge. So how much power would that be worth? This is what's shocking. It was worth about 10.

[00:12:33]So we went from like a 736 to a 746. And by the way, this is across the board.

[00:12:38]What I'm doing right here is I'm showing you the best run we ever got without the ice bags on it and the one run we did with the ice bags. So, it looks a little dis little skewed, but it's still you could tell it's up quite a bit. It's if you do back to back from what we did, which I forgot to get that print out, you'll see it was up the entire way by the same amount. So, it gained universally throughout the whole thing.

[00:13:00]I'm just showing you the best without the ice bags and the one run with the ice bags. So, definitely cooling the charge was worth something. So, now I know it's worth about 10 horsepower to cool the charge. How will the old carburetor stack up, right?

[00:13:15]Um, the airfield ratios, by the way, Aaron's a whiz at this and I'm watching this because several times Aaron wanted to stand outside and listen to how it's running. So, I'm watching it do its correction. He's correcting like zero from zero to 2% in some of the runs.

[00:13:30]They were like spot on and he's not making any really fuel changes. We tried some different timing and things as well just to get it the best it could be with DI. All right. Then we put the fuel to the carburetor and disconnected the um the direct injection. You might be asking how'd you do that? That's probably a better question for Aaron because I don't entirely understand all the stuff with that. But here's essentially what he did. He pulled out the good pump because the idea of running that pump dry, that DI pump, because obviously we're not going to run fuel to it. Running it dry and you got a piston that moves up in there is probably not ideal. So he used a junk one that he took some of the guts out or something on and put that one in there to put it in its place.

[00:14:10]disconnected the um harness that would go to the injector so they're not trying to fire obviously because that would really mess things up. And um that was how I did ran our fuel to this carburetor. I hadn't touched it since I took it off my 406 dynam. I did warn them. I said, "Man, this thing was running really, really lean on that 406." So I don't know why it was doing that, but it was running really lean.

[00:14:30]Well, guess what? It was running really lean on that, too. So the very first pull, so remember we were at 736 was our baseline.

[00:14:39]The very first pull on this.

[00:15:06]We're like 701 701 with the carburetor. That's a 35 horsepower loss. That's pretty dramatic.

[00:15:17]And torques down about 10. We went from like a 570 to a 560.

[00:15:22]Anyway, this was on was whailing, which honestly I'm surprised they didn't pull back on it and we didn't stop, which I'm glad that they didn't because it did give me a chance to learn something. Um, it's 14 140. Okay. I don't know anybody else that runs 140. The targeted air fuel ratio when they're doing DI is 12.8. So, if you're wondering if having too much fuel in that intake passage might have an effect on it being 14s. Oh my gosh. A little scary. So, we did another we went up uh I think from 90 we don't 10 jet sizes and then still 14.

[00:15:59]Something's wrong with the carburetor.

[00:16:01]Uh and then we're backing off at this point early before we get in the runs.

[00:16:05]And then we changed high-speed air blades. 14 still. I will say we pull off the back bowl. There was a set screw sitting in it. And I think it came out of one of the metering blocks from one of its transfer passages. You know what's amazing though? If you're ever thinking like carburetors aren't great.

[00:16:19]They you know they don't start up. You you old guys don't know what you're talking about. Started right up every time. And a matter of fact, this carburetor slamming it right open right into the pool. No problems at all. Kind of shocking.

[00:16:34]However, we're like, "Ah crap, this thing isn't going to really work." And we're down. The best we got to was about 710. So, 26 horsepower down from the DI and still about 10 foot-lbs of torque.

[00:16:46]They have a quick fuel 1300 cuz this is a 1250 carburetor in case someone's asking. We went to a 1350 or something quick fuel. We really only got to make one run with that because it absolutely hated when the secondaries come open.

[00:17:12]Ollie, slam it open. We're good to go.

[00:17:15]The quick fuel, you run it through the beginning part, everything's cool. As soon as this opens the secondary, as I'm watching it squirt, it goes dead lean and tries to die. We didn't able to make one pool. It didn't really pick up.

[00:17:26]Here's what's amazing, though. The pool it's making is 12.8. It's almost identical to what the DI is doing as far as air fuel ratios. The strange part, it was within like two horsepower of this thing. That's 14s.

[00:17:44]What? I don't understand it. But it was that that crazy. You could almost overlay them because that wasn't good enough. Um Aaron, because we're at Co, they have a Da Vinci carburetor there.

[00:17:56]We had to twitch some things because its needle and seat was hung up and it had some it was just had some sticky stuff.

[00:18:01]So they robbed the bowls off this, put it on the Da Vinci. It's a 12 1200 because they do buy venturi size and the blade size. Make another run >> run. It's 12.8. It's matching the DI.

[00:18:32]It's making the same power as a 140 on with this one. I don't understand that.

[00:18:37]I really don't. But um the air fuel racers are spot on. 128 and it's consistent too. It's not like it's fluctuating. Both these carburetors like it 14 straight. The 12.8 straight. So anybody that thinks that you have a way off carburetor. This one's way off and then it's lean. But it's worse if you have a carburetor that goes really rich then really lean then really rich and then really lean. This was both of them all of them are consistent that way. So, this right here, hopefully you're watching this as I was describing it, but what you're seeing here is the dino graph that shows the difference. You'll see all the carburetors that are there, and you can see the difference in the power. It's pretty dramatic. So, the black line, obviously, that's the DI.

[00:19:18]It's It's ruling the world. The red one's the quick fuel. The other ones, which are really hard to see because the only reason why you see the quick fuel is at the end where it drops off.

[00:19:28]the others, the this one with all the jet changes, the Holly and the Da Vinci, virtually identical.

[00:19:38]So, what have we learned? It turns out having the fuel in that intake passage hurts power. Absolutely hurts power. We also know that the cooling effect gained power. So, if we if it wasn't for the fuel cooling this, it probably would have lost even more from the amount of fuel taking up. But obviously, we couldn't do that. So, we get some information. We've learned some things.

[00:19:58]We've definitely learned that cooling helps. We also definitely learned that the fuel in the port does not help. So, that is something to think about. Um, one of the other things I want to point out with is that's a 320cc runner.

[00:20:16]That's so big. I would have thought for sure the carburetor would helped it because that fuel there's enough volume to take it up. But the other thing could come up too is that it doesn't have enough vacuum to pull the fuel from the boosters. These are nice annular boosters in this Holly by the way and so was in the Da Vinci, but it still pulled on the others. So I don't know. Um it was definitely gives you something to think about. And all I could say is yeah, it it's carburetor lost. It did. It absolutely did. Now if you're talking about cost, that's a different story, but yeah. And not to mention LT engines. Wow. I mean, really? Wow. Um, GPI does make because I asked them, they do make a smaller head because they can't make obviously because of the casting on the stock GM casting. It's already big. You can't make a a port smaller without filling it with epoxy, which maybe you could actually do that on a GM one because if there's no fuel running through, I don't really have to worry about the fuel taking the epoxy out and washing it out.

[00:21:17]But anyway, they use for their smaller ones, they use a C head so it starts off smaller and you can make it smaller and move more air too. So, but this just happened what they had for it. So, thanks to them for letting me test it.

[00:21:29]Um Aaron for coming down because I know he's very busy running the company and everything. And um Justin had a lot of stuff he had to get done, too. So, thanks for that. Um Brian's a big tuner there. If we'd been doing HP tuners, they would have probably had Brian there, too. But Holly seemed to be working right for this. Now, I did not talk about all the negatives and I can already hear in the comments. So, if you don't want to hear the negatives, you can just tune out now and I totally hit it. But if you want to hear some of the negatives, I'll give you this. Before you think direct injections, like the cat's meow, there are obviously drawbacks. Um, the direct injection can only put in a certain amount of fuel, period. So, that limits the amount of power you could possibly make. So, even though we tested on gasoline uh C10, if you were to test on E85, chances are the difference would have been bigger as far as a power difference, and I think that's why Brian Tulie and Scott Clark, they tested on E85 because it makes a difference look bigger, but on gas it's smaller because the E85 takes up more volume in the runner. However, back to the DI though, that pump can only move move so much fuel. So, if you're an NA guy and you're strictly NA, it's probably a W. It's it's not probably it is a win to be that way to run DI. It's should be a win.

[00:22:41]However, if you're and I and I'm a true I like NA, but power outers are where everybody's going. Okay, boost. That pump can only move certain amount of fuel and you're going to want to run E85 and you're going to run a lot of it if you're under boost or even methanol and you're on a lot of boost. There's not enough. It's not just the injector. It's the amount of time. So the time it takes to spray that amount of fuel in there is not enough not a lot. Especially the higher RPMs you go. So you you can only put in so much fuel. So if you're under boost, there's only so much boost you can make before you have to add another fueling device like port injection. And that's why like some of the boosted GM stuff, they've still got direct injection probably for when they're cruising around and they'll throw it in the port whenever it starts getting up there in power. So that's a disadvantage. The other disadvantage is if you look at this head here that I have here, this is a stock um LT head.

[00:23:35]This is the intake ports. They are carboned up. How can carbon get in an intake runner that has no fuel that runs through it? Reversion. So, one of the disadvantage to that too is when you have DI, which this is one thing I want to test. I'm not rich, but I hope to test this. One of the things that happens, all this carbon that builds up, it's really bad on the back of the valves. Eventually, I'm going to tear this to head down. I'm going to flow it exactly it is with all the carbon buildup on it because I think this one's got like 60 or 70,000 miles on it and flow it that way. Then I'll clean off the carbon, flow it again. The question really remains though is what if you took an engine that had say 70,000 miles because I I really like to do this. I don't have the money to get an LT engine, but I'd like to buy a junk one um that has like a lot of miles, like 100,000 or something. Dyno it exactly how it is. take off the heads, clean off the valves, and redyno it. Because my thought is as the carbon builds up on the back of the valves, the air flow is going to decrease. So, you're going to lose power because of that. Port injection still has carbon buildup, but because the fuel spraying on it kind of cleans it. There is no fuel spraying on this valve. So, the DI kind of that part's not so well. I've also heard other things you can argue too because the fuel does act as somewhat of a lubricant on the seats itself. So maybe the seats itself last longer on a nonDI head and we could get in that stuff on and on, but just some things. Anyway, hopefully you guys got something out.

[00:25:00]I'm very impressed with the DI situation. The LS LT platform is wow and uh very superior. If you have any question or any comments you want to put in there, feel free. Um I'm not done with testing on as far as stuff goes.

[00:25:14]This just gave me more questions. But for now, yeah, car loses. Guys, remember I am no Superman. I did race Super Boy.

[00:25:24]I don't port cast iron heads. I don't respond to Facebook or Instagram messages. The best way to reach me is through email [email protected].

[00:25:31]Again, thanks to the GPI guys and guys. You guys take care.