60 mpg or bust... '97 Paseo build

Discussion in 'Toyota' started by Daox, Mar 18, 2008.

  1. Daox

    Daox Well-Known Member


    I've had the Paseo a few years now and have done several modifications to it. The 1.5L 16V engine currently has a shaved and ported head, bored throttle body, underdrive pulley, cold air intake, and a header with performance 2" mandrel bent exhaust. I built it to get more power out of it, and that was fun. But, now its time to get more mileage out of it.

    If you click my signature and/or look below you can see that I'm averaging mid to upper 40s out of the car as is in winter conditions. The last tank was a hair above 50, and the goal for this summer is 60 mpg.


    So, where do I start?

    First off is probably aerodynamic mods. They are cheap and easy to do. The car sees 95% highway as its my daily commuter vehicle, so this will be the most cost effective place to start. I am starting with something that is reasonably good with a drag coefficient of .32 and a frontal area of 19.0ft^2 (1.77m^2). I'm thinking of mosly using a bellypan of sorts to smooth the underbody airflow. There isn't a whole lot of area up front to block for the grill, but I'll be looking into that as well. There is a possibility of rear wheel skirts, but I'm not sold on this just yet. I've also been looking at GM's EV-1 electric vehicle with a Cd of .19 and looking to immitate its front bumper to some extent. Some aerodynamic testing will need to be done to see where flow seperation occurs. The rear spoiler may have to go. I'll also looking into front wheel air deflectors once the belly pan is done.


    Of course there are other areas to work on too. Here are a few other things I'm looking into:

    continue to refine driving technique
    remove underdrive pulley (did this last weekend actually)
    go back to stock throttle body (already have this, just need to install)
    new exhaust (will definitly have this come summer)
    stock or new intake
    new head with some port work done

    The first 'mod', if you even want to call it that, was actually done a few weeks ago when I put the underbody panels back on the car. I had remove them a long time ago when I was doing engine and exhaust work and never put them back on. Unfortunately, its so freakin cold out I didn't do any before and after coast down tests to see the effects of the panels.

    Stainless fasteners... priceless in Wisconsin's salty road conditions.

    The panels.


    After, and a bit more aerodynamic I'd imagine.
  2. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    I'm looking forward to seeing your results, Tim! This should be good. :)

    You mentioned regearing -- what are you up to on that in particular?
  3. Daox

    Daox Well-Known Member

    Pretty soon I'll be replacing the transmission in my Tercel which is a 4 speed. I should be able to swap the differential from it into my Paseo's 5 speed. Since the Paseo is considered more of a 'sports' car, it got higher gearing. This should drop the rpms down a bit.
  4. diamondlarry

    diamondlarry Super MPG Man/god :D

    I'm betting the transmission swap will be worth a few mpg all by itself. Over at Saturnfans.com someone did a 5th gear swap on a Saturn SL2 and picked up nearly 20%. They went from the SL2 gearing to one from a '98 SL1. I predict you'll hit 60 mpg and then some. I do have a number for a guy in PA...:D
  5. FocusGuy77

    FocusGuy77 Guy with Focus

    Why take off the udp? It reduces parasitic losses.
  6. Daox

    Daox Well-Known Member

    I've heard negative things about the pulley's effect on engine longevity. Specifically because it doesn't have any form of vibration dampening. Also, with the other mods I plan on increasing engine off durations and don't want to have to worry about the battery not being charged enough because the alternator is being underdriven.
  7. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Valid concern. My battery just barely stays at 12v during summer months, and drops to the low 11's in winter, due to headlight usage. Simply put, I'm FASing over 1/2 of the driving time, so the alternator is already at 1/2 duty or less. Underdrive would reduce that to a point that's unusable.
  8. Maxx

    Maxx He who posts articles

    The first thing I was going to say was tranny, but you beat me to it. You could consider lightening your pullies/flywheel - just be careful the the lightening is even across the 360. Also, lightening in general - remove sound deadening, carpet, back seat (if you can call it that), etc...

    Also, this winter I used a radiator block (corregated plastic zip-tied in front) and a warm air intake to up my mileage a bit. My WAI died because just as a test I used plastic pool hose which was fine for my 20 minute commute, but got melty when my girlfriend borrowed my car for her 45 min-1 hour commute. Anyway, I had it positioned to pull air right from between the exhaust manifold and the engine, which on my car is conveniently in the front, right next to the dip stick. That was good for +6-10 degrees in my coolant temp during a 20 min commute.
  9. shifty35

    shifty35 Well-Known Member

    Sounds like some interesting plans in progress... my thoughts.

    The final drive swap should be an easy way to pick up a few (at least!) mpg from the lower cruising RPM in every gear.

    Typically, mods that add HP typically do one of two things:

    1. Increase high RPM torque at the expense of low RPM torque or
    2. Improve overall engine efficiency

    Clearly any mod falling in category 1 is power at the expense of fuel economy, while 2 should *increase* fuel economy as well as power.

    Cold air tubular intakes with conical filters (that are designed well) are tuned to a particular length to reinforce air waves in a specific band. If you have time on a dyno, you could play with various lengths to pick something that adds torque at a lower rpm (around 5th gear cruise particularly!) Definitely reroute it so it picks up warmer air though.

    The ported head will also increase efficiency everywhere. You may want to shave it more to bump the compression ratio (if piston replacement isn't feasible).

    The overbored TB is probably overkill for your engine without a higher lift / duration cam. It will give you more WOT airflow at the expense of air velocity. Ditch it.

    I'd say *keep* the header if it is a 4-2-1 design with fairly short primaries.

    I'd also say stick with the exhaust if it is not bigger than 2".

    Underdrive pullies without a harmonic damper are proven to destroy bearings. Your battery needs every ounce of charge it can get. Ditch it.

    You may look into lowering it an inch or so for the improved aerodynamic properties.

    Aero mod away... delete those fog light openings, add air dams for front and rear wheels and rear wheel skirts.

    I'm looking forward to your progress - I'm about to "acquire" a 92 Civic Sedan with a toast motor I plan on experimenting with. :D
  10. Daox

    Daox Well-Known Member

    Thanks for the suggestions and comments guys. I'll try to explain some of my reasoning and further explain the modifications.

    Keep in mind 95% of my daily commute is highway. Half is in a 55 mph zone, and half is in a 65 mph zone. I P&G the entire way using 65-55 (50 when possible) in the 65 zone, and 60-50(47 when possible) in the 55 zone.

    The regearing I'm not expecting the world from. My current peak torque (measured with a g-tech) occurs from about 2200 rpm to 3000 rpm. Now, at 65 mph the engine is turning just a hair under 3100 rpm (47 mph is the low limit for 5th gear @ 2200 rpm). This is pretty close to ideal. With the new differential it drops me down to 2750 rpms @ 65 mph, and increases my low limit in 5th to 52 mph. This kinda messes up my 55 mph zone that I usually coast down to 50 mph in. So, in order to counteract this, I need to shift my peak torque band lower. This is where the stock throttle body and new intake come into play along with the new exhaust.

    The intake that is currently on it is not incredibly oversized, and is quite long. I didn't do any testing with different lengths, but specifically went this way to maintain more low rpm torque. It is made of a 16 gauge 2 1/8" OD stainless mandrel U-bend. I'd have to say its around 36 inches long (probably too long). The stock plumbing is quite a bit shorter between the airbox and throttle body, but slightly smaller diameter (probably around 2"). My only reservation with going back to the stock plumbing is that it is so short. The stock intake will be tested versus the current one with the g-tech. Warm air will definitly be looked at when I am looking to develop the new intake should I need one.

    Like Shifty said, the throttle body is overkill unless I'm hitting high rpms @ WOT. As mentioned the highest rpms the engine sees is 3100 rpm. It'll be replaced as soon as it gets warm out. I'm interested to see how this seemingly small change will effect the torque output.

    The header is a very cheap and poorly made Pacesetter header. Its noisy and poorly designed. I have a 4-1 header made by Hotshot, but the primaries are on the large side (1.5") for low rpm torque. I'm not sure if I'll go with that or the stock manifold. The rest of the exhaust is falling apart from the beating it taken during the few winters it has seen. It needs to be replaced anyways so I'm probably going back to near stock 1.75" piping.

    The head is a more distant mod, but one I'm looking forward to. The stock head is a run of the mill 16 valve head with a stock compression ratio of 9.4:1. I think with some port biasing and some combustion chamber work to promote more swirl that compression can be bumped up quite a bit. The current head was shaved .025" and was quite happy without any other work but porting done.
  11. Maxx

    Maxx He who posts articles

  12. Daox

    Daox Well-Known Member

    That would be great if I had the cam information. Unfortunately, I don't.
  13. Maxx

    Maxx He who posts articles

  14. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    :eek: Looks like an intake of 60+ inches to get below 2,000 rpm!
  15. shifty35

    shifty35 Well-Known Member

    Ever seen a truck intake manifold?

    The Insight's intake manifold all contorted to get runner length for low RPM power.
  16. Daox

    Daox Well-Known Member

    Interesting discovery. I've finally gotten my scangauge back from being upgraded, so I put it in the Paseo. Water temp was a big thing I wanted to monitor with the vehicle so I could see how far I could go with grill blocking. To my amazement the car is running at 190-200°F already! As far as I know it has a 185° thermostat. I'm not sure what temp the fan kicks in. I'll have to look that up in the service manual tonight and double check the thermostat temp.

    So, it doesn't look like I have much room to work. However, I plan on making room to work. How? By improving the efficiency of the stock setup. Currently, air enters the front bumper through the main opening, and two small side openings. It then goes wherever it wants and runs into many different things. I'm thinking that I will add some deflectors inside the front bumper to direct airflow directly over the radiator. This would stop air from going around the radiator and thus provide more consistant cooling. The image below is a top down view and kind of shows what I mean. The two small outer vents will eventually be covered.

  17. Maxx

    Maxx He who posts articles

    My car with a slightly open grill block runs 202 (I think it was 198 before block), with WAI was running about 208-210. An that was last month (Feb in CT).
  18. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    My cooling fan comes on at about 205F. Found that out by running it that hot, and the fan came on. You might try a temporary block just to see. ... or just wait until summer and find out then.
  19. Daox

    Daox Well-Known Member

    If the car is supposed to run that hot I'm fine with that. But, its still cold in Wisconsin, and I'm a bit leery of summer. In either case the deflectors will give me more consistant cooling which will allow me to decrease the size of the opening in the bumper and that will decrease aero drag.
  20. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    On my civic, the radiator is only the right half of the opening. The left side is for the AC, so I leave that blocked full-time. My block is in quarters, so I can open half or all of each side as needed.

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