My FE/Performance Project
I built my entire engine around fuel efficiency and performance. When I started this project over ten years ago I made a list of major factors that would aid in the engines efficiency.
Here's my list in the order of importance. 1) Low numerical "Throttled BSFC" numbers. 2) Lean Burn Technology. 3) Fast-Burn Head design. 4) Reduced Pumping Loss Engine design. 5) High Fuel Atomization. 6) Programmable EGR system. 7) Advanced PCV system. My list of modifications to reach these goals. 1) Low numerical "Throttled BSFC" numbers. My goal was to be able to reach a BSFC number of .35 or better (.35 BSFC is based in lbs) at part throttle. At one point I had the idea to decrease the engine size to under a liter and use a smaller engine and run at a higher load with a better BSFC number to help with FE. But then after talking to Ben Strader of EFI University and a few others, I decided against it. I understand that car manufacturers base their engines BSFC at high load or part load. This will give them a better BSFC number, but it doesn't tell the whole story as far as the consumer driving down the freeway at light load. IMO very light load freeway driving is by far the most used by the consumer. One other thing I would like to address on this subject is I see a lot on other forums that ones thoughts are you will achieve your optimum BSFC at heavy load. So we feel like we need to run the engine at a higher load to get a better BSFC number. I agree to some extent , but keep in mind all EFI systems have accelerator pump values that are read off the TPS. The accelerator part of the EFI program does what carburetors did with their accelerator pumps in their day. It adds fuel based on the speed of the throttle plate being opened to prevent a lean back fire. Usually the EFI throttle pump system will have three RPM opening points with a decay setting on all three. It will also have a coolant base adjustment built into it. All three will add to fuel injector opening time base on %. So back to my point if you are trying to to get to the ultimate BSFC number with high load your also dumping more fuel in through the throttle pump part of the program. Something that is not included in the posted BSFC charts of different engines. Now lets look at the BSFC WOT and or high load part of an engine. All engines have to rely on the fuel for thermal management. Incoming fuel is one of the largest factors for cooling down the combustion temperature that takes place durning the intake cycle. So at high load or WOT the engine is wasting a lot of fuel just for cooling purposes only. This kills BSFC numbers. Plus at high load you burn more fuel due to a higher VE. So more fuel results in more heat, more heat means more fuel that's needed to cool combustion temps. One other factor is at a high load the air velocity is much slower. Slower velocity means less atomization of the fuel. So now more fuel is needed to make up for poor atomization due to lean spots and overly rich spots in the combustion chamber. So as you can see I was left with a problem when I wanted to introduce my next modification "Lean Burn" There was no way i could run 20:1 + A/F at high load and keep the engine from detonation. So I had no choice then to concentrate on light load great BSFC design. So that brings us to... 2) Lean Burn Technology. Lean Burn Technology goes hand in hand with great BSFC numbers. My thoughts were to use as little fuel possible to produce 20whp. To do this I would need a BSFC number around .35 so lean burn was my only option. I came up with a prechamber design that would be able to ignite and start combustion with A/F ratios in the stock combustion area around 25:1 to 30:1. At these A/F ratios the heat is reduced (good) and flame speed slows down drastically (bad). Plus NOx levels increase(bad). One thing I found out is at very lean conditions atomization improves a ton. But back to heat. I noticed in my data logs that my water temps drop when it goes into lean burn. This was a relief because the higher A/F ratio requires a slight higher load. This is also where the turbo comes into play. With a higher load with an turbo engine makes more boost and reduces pumping losses.(good) But now the bad, flame speed decrease and now I have to start the ignition timing sooner. So that brings us to... 3) Fast-Burn Head design. My Honda multi-valve pent-roof design has a fairly fast burn rate when it comes to head design. This helps with increasing flame speed so less ignition timing is required. So that brings us to... 4) Reduced Pumping Loss Engine design. My main contributor to helping with pumping loss is the turbo. Plain and simple it creates a higher then ambient pressure so as the piston cycles downward its being aided by pressure acting on it durning the intake stroke. But what about the compression stroke? High compression engines will take more energy then lower compression engines when it comes to the compression stroke. My engine is around 7.5:1. You can turn it over to where it feels like there isn't any spark plugs in it. So at very light load it would turn very easily. One other thing I think that is happening is there are some left over exhaust gases that will aid in NOx from a very low compression engine. So that brings us to... 5) High Fuel Atomization. All I have done here is I'm running a higher then normal fuel rail pressure 60psi. to help aid fuel atomization. 6) Programmable EGR system. 7) Advanced PCV system. These two items are what I'm working on now. The programmable EGR system will be where I can control how much I want to recirculate. The advance PCV system will have an electric evac system to reduce crankcase pressure down to almost a vacuum. This will help with sealing the lose ring pack and reduce pressure in the crank case that will help when the pistons are cycling downward. Well this is my own home brew engine design and so far it has been successful. I have gone against the grain on a few other ideas. But sometimes thinking outside the box is necessary no matter what the out come good or bad. My goals are to achieve 75mpg @ 65mph. So far my personal best has been 74mpg@58mph. Make over 450+ whp. I have made 418whp. Run a 10 second ET in the 1/4 mile. Personal best of 11.8@130mph street tires. Of course it doesn't get great mileage when its running in a performance mode.;) My mod list. Chassis: 1993 Honda Del Sol S Polyurethane Spoon replica front lip OEM 14' steelies Stock port New Skunk2 intake manifold New Zex Stage 2 cam (59300) New Supertech valve springs New Supertech valves OEM 60mm LS throttle body New ARP headstuds New OEM valve seals New OEM retainers New OEM valve keepers New OEM headgasket New OEM valve cover gaskets New OEM cam seal New OEM timing belt New OEM timing belt tensioner New OEM alternator belt D16z6 block New 75mm YCP vitara pistons New Eagle rods with big bolts New ACL main bearings New ACL rod bearings New OEM main seal New OEM oil pan gasket New OEM water pump New OEM oil pump New OEM oil pickup New OEM main bolts Drive-train: D16z6 tranny with 1st gen OBX LSD New Action 2md clutch New OEM axle seals (located on tranny) OEM resurfaced flywheel New Energy Suspension shifter stabilizers Brake and Suspension: GSR front brakes* GSR rear sway bar/LCA's* Strut bar welded into trunk* Koni Yellows* H&R Race springs* Exhaust: Top mount turbo manifold w/custom up pipe down pipe. Holset HE351CW Turbo RRP 2.5 inch ECUTOUT for track and then connected to STOCK exhaust for quiet street drive Turbo Setup: Holset HE351CW Turbo Ebay intercooler Ebay SSQV BOV Ebay intercooler piping Hallman Pro MBC Fuel Management and other MISC: P28 with Neptune RTP PLX wideband with gauge New Motorola 2.5 bar map sensor New Precision 780cc injectors OEM resistor box Walbro 255LPH and inline 255walbro for E85 Autometer Boost gauge Autometer Oil pressure gauge Also keep in mind that this engine is not anywhere near stock anymore. 1)I'm running a very low compression around 7.5:1 to help with pumping loses. 2)Thermal-Coated bowl shape pistons. To keep heat from transferring into the piston and the bowl shape to help create swirl and centralize the flame front. To help with the boundary area of the piston. 3)Extremely loose piston to cylinder wall clearance. Better mechanical efficiency. 4)Large piston ring gaps. Better mechanical efficiency. 5)Modified combustion chambers for lean burn. To provide a fuel rich area to help ignite the fuel and air.To increase the size of the flame kernel. To accelerate flame speed durning lean burn. As for city driving. I haven't a clue. I'm still working on light load freeway driving. I want the car to give the same results no matter who's driving (very user friendly) without the need for Hypermiling. |
I got some more work done. Clean up pics and welded a new return 12AN in the oil pan and O2 bungs welded in.
https://www.fuelly.com/attachments/fo...efed9a9379.jpg https://www.fuelly.com/attachments/fo...350de5e513.jpg Built a 4" v band flange flange cap. https://www.fuelly.com/attachments/fo...47c2d4ed01.jpg https://www.fuelly.com/attachments/fo...309017f19a.jpg https://www.fuelly.com/attachments/fo...e6b610d628.jpg https://www.fuelly.com/attachments/fo...a1357944d0.jpg https://www.fuelly.com/attachments/fo...6ef0b41810.jpg https://www.fuelly.com/attachments/fo...5d5904f9ab.jpg |
A couple questions...they may sound dumb, but bear with me.
How large of piston ring gaps? I can remember a car I had years ago with large piston ring gaps, (about 1/8"), gas mileage wasn't bad...Plymouth with a 383 ci engine, about 18 mpg, about 30 miles/quart of oil. Also you mention extremely loose piston to cylinder wall fitting. Any piston slap? How will this affect longevity of the engine? |
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The piston ring gaps are .018 on the top comp ring and .019 on the second ring. The cylinder to wall clearance on this setup is .006. This will affect long term engine life and is one of the hurdles I'm trying to figure out what to do? As of right now I need the extra piston to cylinder clearance and ring gap for the HP I'm running. It doesn't use any oil between oil changes (every 2K) but I know it won't be your typical Honda and run for 200,000+ miles.;) I plan on building another engine like this one but it will be a 1.5L and with more stock type clearances. But the 1.5L will only make around 250whp. Oh and to answer your question on piston slap.. YES it sounds like a diesel on start up. I'm going to install a engine block heater and run it all year round. LOL |
So you decreased the compression ratio yet improved the overall mileage?? So tell me, how DID you achieve that 75mpg while cruising at 58mph? What kind of mpg can you get at 65mph? Any aerodynamic mods? Were you doing pulse and glide? The reason I ask is that it seems counter intuitive to go a lower compression ratio opposed to a higher one. Did you choose a lower compression ratio because you knew you couldn't modify the computer's programming? Or can you? I ask this because the Insight and the Geo Metro both have very high compression ratios (11:1) so you going the opposite direction seems strange. Yes I am aware that you have the low compression ratio for the turbo but 7.5:1 seems awfully low and usually cars run 8.5:1 when turbo equipped, maybe even 9:1.
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Wow, that's quite a project. It sounds like you've really put the effort into studying this stuff that most of us would never do!
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- At (or very near) WOT, EFI will go to open loop, ignore O2 sensors, using rich static fuel tables instead of trying to measure perfectly - At any other throttle level, EFI will try to keep the air/fuel ratio perfect I haven't been able to experiment with that because my car doesn't seem to ever go to open loop or enrich, reportedly because its wideband O2 sensor allows the EFI to always stay in closed loop. Either way I can't argue with results; I slam the gas pedal to the floor after every shift and get great fuel economy. I don't think the way I do it would work with most other cars. Quote:
Also, how would 3 and 4 reduce pumping losses? If you mean piston-cylinder friction, I consider that as a separate issue from pumping loss. One other thought: Are your pistons and connecting rods lightweight to reduce reciprocating loss? |
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Yes, it does have throttle by wire. That would be the first time I've heard of throttle by wire being credited with not using open loop, but it certainly sounds as reasonable as the wideband O2 explanation. As with your S60, my Rabbit is only open loop for a few seconds after a cold start.
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My O2 is just along for the ride and does nothing other then give me real time readings and data logs. The 75mpg was on a road trip over 500 miles of driving at a steady state cruise condition with no pulse a drive. Yes I can and have altered my stock ecu settings using Neptune engine management. My engine runs in open loop all the time by running off my preprogrammed fuel and timing etc. maps. My sons car has the same engine but with stock 9.8:1 compression and with him running at 17:1 A/F and me running at 17:1 his mileage is not as good as mine. But of course when I take it up to 22:1+ mine is way better. |
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I need to fix that it should have read greater mechanical efficiency through friction loss. My pistons are lighter but the rods are heavier. So combined they come out to be a little heavier. |
Wow! Great project. My car has several similarities to yours:
I have 7.9:1 compression, pentroof combustion chamber, dished pistons, turbo, programmable ecu with lean burn. I've thought about rebuilding my engine with higher compression, but it's still running so I keep using it as is. I just wish my results were as good as yours. Have you thought about using beehive valvesprings? They've just become popular in my corner of the tuner world. It seems they allow lower seat pressure, which reduces valvetrain friction, while still keeping the valves from floating or bouncing at high rpm due to the harmonic damping abilities of the variable diameter. |
Oh yeah,
Oil squirters keep pistons cooler so you can run tighter piston clearance. Does your engine alredy have them? Is there any way you could swap in a taller 5th gear from another drivetrain? Have you considered using a custom cam with late intake closing to produce a Miller/Atkinson cycle effect? |
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I had beehive springs on my Turbo 93 Talon AWD. They do work great!!! Compared to my Talon the Honda spring seat pressure is lower then the Talon's so I stayed with the ZEX springs. |
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I do need a taller 5th gear so i'm going to be swapping in a VX 5th gear. I'm looking at having a custom cam ground to take advantage of the Miller/Atkinson effect. When I do this I will probably have to increase the compression though? |
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When the car is in lean burn mode the AF ratio varies with load. At medium loads it's around 17.3 to 17.8. |
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They share the same 1st gear 3.25 2nd gear 1.90 3rd gear 1.25 4th gear.909 final gear 4.250 ratios the only difference is the 5th gear .702/.750. I know its not to much of change but my plans are for only a 5 mph increase at the same rpm using the .702 with a taller tire.(so I can cruise at 65mph freeway speed) I tried a VX tranny with my engine combination and it actually was a lot worse then with the Si trans. Now if I had better aero mods I could use the VX transmission at a higher mph and it would probably work very well. |
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Thanks for the info!!!:thumbup: |
I finished the waste-gate dump tube and oil return line and all three O2 sensors are hooked up.
https://www.fuelly.com/attachments/fo...665b139f53.jpg https://www.fuelly.com/attachments/fo...d53b26d7c3.jpg https://www.fuelly.com/attachments/fo...673dc2189c.jpg |
Looks nice! Is the oil return line close enough to the header to need heat wrap? It looks close in the pic.
Nice taper on the collector, too. |
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Braided stainless. Do eeeeet. EDIT: wanted to chime in to tell you, your exhaust is ridiculous. Why did you choose to do it that way? Clearance doesn't look to be much of a factor if you had dumped it under the car... How will your wideband read accurately. What sensor is going right there closest to the turbine? It's going to melt/fail regularly. |
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Your edit response.... I built it this way because the turbo has a 4" outlet. It doesn't dump under the car. It hooks to the stock exhaust. The pics above shows the 2" down pipe not hooked up yet. All the pipes are bent and ready to go, I just ran out of time. https://www.fuelly.com/attachments/fo...8c66db61ce.jpg Pic showing how its all tucked away with no longer a low ground clearance issue.;) https://www.fuelly.com/attachments/fo...16b54882a5.jpg The 4" up pipe is for when i take it to the track. I will then run the 4" up pipe open. When I run it on the street it will be closed with the 4" v-band cap I built. The 4" down pipe would be a pain to make but it could be done. But then you have the problem with ground clearance. My car is 2" lower then stock and the first driveway with any amount of angle would of taken it out. The O2 sensor will be fine also. I've run one closer then this on my DSM and have never had any issues with failure or miss reading(over 50k miles). Both this car and my other have two wide band O2 sensors and they read the same. One O2 sensor as close as this one and the other about 20" away from the turbine. I also do have a Innovate O2 HBX-1 heat sink. Your next hate post will be why did you go with a turbo that has a 4" outlet. I will answer it before you waste your time posting. This turbo will give me the means to run a 10 second 1/4 mile and make over 450whp. It will also handle the anti-lag that it will be subjected to. Plus it has a very good spool response and will give me the light load that I need to get over 75mpg. |
Nice build! I would also like to know how you got 74 mpg. What size tires were you running, and what aero upgrades do you have? It seems counterintuitive to have large ring gaps with a turbo, but I'm a N/A guy.
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I have extreme doubts that during a WOT track pull, while your manifold is glowing red, that the oil return line will survive. More power to ya if it does.
I didn't know that 2" pipe was going to be exhaust routed under the car, I thought it was just some weird dump. Still, about the 2", why did you angle it opposite to what looks like would've been more free flowing? I've seen many y-pipes redone and cars make more power on a dyno just by smoothing out the merge. Your merge is backwards to what is conventional. Is there a reason? Since you mentioned my future hate post about a 4" turbine: Why didn't you just go twin scroll instead? |
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The main reason for the great fuel mileage is a prechamber I built so I can run as lean as 30:1 A/F. My tires are LeMans SR P195/60R14. Aero up grades is the car is lowered 2" from stock. With a grill block. My ring gaps have to be this loose due to the fact when its raced the extreme combustion temperature can cause the ring ends to but against each other if the gaps are to tight. |
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Also I'm not to concern about loss of HP with the odd configuration. It only has to make 50HP when its ran in a street mode(4" up pipe capped). The reason I didn't go with a twin scroll turbo is one price, I have three HE 351CW turbos and all of them where given to me for free and also this turbo has been proven to make the power to run mid 10's @ over a 135mph with this engine. Also this car looks and sounds completely stock when I'm running through the stock exhaust system with the uncut hood. |
First off, nice build.
But I agree with the oil return line. Why not at least do it in braided stainless? It would not cost more than probably another $20 or so in that short a length and have a lot better chance surviving if it happened to get a bit closer to the manifold. |
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OK shes running again. Everything looks great so far.
The exhaust system is working out great!!! Very quiet and stealthy. I'm still going to build a few heat shields(upper radiator hose and between the head and manifold on the dist. side) |
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Are you going too give that engine better spark?
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500whp 1.6L SOHC Honda's using stock ignitions. EDIT: Pic of the Neptune software https://www.fuelly.com/attachments/fo...71136294ed.jpg |
Ok I'm thinking about going with a different trans oil.(Ams oil etc)
I have been using Honda's Manual Transmission Fluid (MTF) Has anyone on here seen any improvements of FE over Hondas MTF??? |
Thanks for that link. I wish i could see your setup in person! It is exactly waht I would hope to achieve if I had the money, and knolwedge t
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Its taken awhile to build it and more money then I wanted to spend but so far has been worth it. The new turbo setup has been giving me some problems but I think I got it figured out now. My biggest concern now is when I start the dyno testing and hoping that the transmission gears don't go flat on me and hurt the FE side of the setup. Aren't you in Portland Oregon? If so I will be going through that way when I do my next long trip FE test. My goal is to see if I can make it to San Francisco on a tank of gas.;) |
Yeah! I'm in Portland. Definitely let me know when you come through here. I can drive along side you, so you won't have to use extra gas :) Or you could not count the extra gas to meet me somewhere...
Do you know; I'm thinking about heating the fuel line to help combustion. Some people said it didn't work, but they didn't have standalone EMS. I can, of course lean it, so the heated fuel would make a bigger difference. Also, theoretically, Acetone loosens the bond of Gas molecules for better atomization. I do see a FE gain when I use it, but haven't used it with running lean yet. I'm also going to put in an MSD6A, even though I've read it won't do much. I already have it, and it won't hurt. |
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IMHO I think heating the fuel does contribute to better FE. I did some testing last Fall and it look like I saw some gains around 4% in FE. I'm going to make a better system this year. The one I was running last year was kinda ghetto but it worked. I haven't tried the Acetone deal yet. |
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