Bus EFI Modifications

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Derek May
Posts: 217
Joined: Tue Oct 02, 2001 1:01 am

Bus EFI Modifications

Post by Derek May »

Old bus, good bus, needs new engine. Has FI, like FI, don't want to fiddle with dual carb linkage. Looking at Jake Raby's big bus engine, but his site says stock FI does not deliver enough power. Someone suggested using stock bits, bigger bosch injectors, and an after market ECU, such as Perfect Power. Anyone done this? Reasonably handy here, can figure out remaping, but don't want to fabricate bits. Want to go with bolt on modifications.

Also curious -- dia of stock throttle body.
Specs on stock injectors.
germansupplyscott
Posts: 887
Joined: Fri Jul 20, 2001 12:01 am

Bus EFI Modifications

Post by germansupplyscott »

you should try posting in either the type4 forum or the fuel injection forum. there are some very knowledgeable people who read and post there constantly. the bus forum is a bit dead.

scott lyons
Derek May
Posts: 217
Joined: Tue Oct 02, 2001 1:01 am

Bus EFI Modifications

Post by Derek May »

will do. Anyone following the chain, check the FI forum.
ray greenwood
Posts: 1941
Joined: Thu Jul 19, 2001 12:01 am

Bus EFI Modifications

Post by ray greenwood »

Hi Derek... A couple of points. Jake Raby knows his engines pretty well. If you actually go with one of Jakes engines when you rebuild....stick with his induction recommendations. He has well researched what works on what he builds. If you are just going back with a stock rebuild...or even slightly modified...there is nothing wrong with using stock injection. In a basically stock motor, it produces better and more dependable HP than most twin carb systems that are available. There are a more than a few things that can be done to make the injection run better than it did when it came on the original engine. Most of them are tuning issues...not many hard modifications...and the FI can produce much better than stock listing. In the hardware dept....get a good cam that works within the stock FI valve timing ranges. This is imperitive on D-type...not quite so much on L-type. Web cam makes a good one for this. Do not run with reduced compression....no less than 8.0:1 no greater than about 8.5:1 on the street. You will actually have less heat issues at these compressions on the bus because the injection works better, the fuel stays mixed better, the engine runs more efficiently. Solid rocker spacers, 911 swivel foot valve adjusters. Get a decent port job...with some bigger valves. Be careful in your valve selection...don't overvalve it. 41x38 ..42x39...I have also seen 41x37. I use the 42x39 on my 1.7...and get great results. I have good port work also. The 39 is probably a milimeter too large to use with stock exhaust... I could probably get a little better exhaust port velocity either with a 38 or moving to a header..but it is working well. The key to making the FI work for you is to start with a very clean wiring harness...and good connections. You need a very good ignition system. A pertronix basic system should be a bare minimum. With the lean burn characteristics...and the higher compression....the ignition was one of the main weak points in the FI motors. In D-jet, there is HP and reliability to be gained in pressure sensor tuning,throttle body upsizing, trigger point tuning and fuel pressure tuning. In L-jet...there is tuning that can be done in fuel pressure, and some minor details in the air mass sensor, and throttle body selection. But to begin with...just get the hardware worked out...good heads, balance everything you touch when you build any type 4 engine. Let me know if I can help you with tuning your FI if you decide to keep it. Ray
vwnate1
Posts: 596
Joined: Mon Jan 29, 2001 12:01 am

Bus EFI Modifications

Post by vwnate1 »

Ray is right here - build a good engine and you'll have plenty of power . the AFC on the 1.8 engine is easy to re-adjust the AF meter for big increase in power plus still passes SMOG tests .

------------------
-Nate
Filth & Greed Imports
(the LAST honest VWshop)
germansupplyscott
Posts: 887
Joined: Fri Jul 20, 2001 12:01 am

Bus EFI Modifications

Post by germansupplyscott »

ray,

where is a source for l-jet tuning info?

scott lyons
ray greenwood
Posts: 1941
Joined: Thu Jul 19, 2001 12:01 am

Bus EFI Modifications

Post by ray greenwood »

You know...Thats a good question. I have never really found a good manual. The Bosch fuel injection manual is a good place to start. I am not sure if and when it has been updated last. What you will get from it is an excellent idea of what each components function is supposed to be...generically ...within the system, as originally designed. The problem with all of the manuals I have read...and haynes FI is one of the least useful...is that they are mainly telling you how to just get it running. They rarely tell you anything about corrective tuning...or tuning for a high performance motor...or a larger capacity motor etc. Don't dispair! Remember a few things. Do you really know how a craburator works? I mean what the fuel and air is doing? How it mixes? Think about what each little part of the carb does. How do air correction jets work? accelerator pumps? Chokes and any other temperature controlling device. Each one of these parts (most of them) have a corresponding part in FI which does much the same thing. Once you learn what each part in L-type does...and how it works internally....you can sit down and draw some parralells. I have had some limited Bosch training. Other than solidifying knowlage of how compnents work...it taught me little about modifying parts...or actually re-adjusting components to give better than factory settings. All of that came from what I have outlined above. When L- or D-type...or any injection is not giving you something you want...think about what component is accomplishing that task. Some components are not adjustable...so find another one from an L-type system that is larger, smaller, faster...or reacts to a different temperature setting. Not trying to sound vague, but what most of the makers of after market injection systems may not have fully realised...is that better faster ECU systems are only a fraction of the answer. EFI is three seperate...yet interacting systems..The air system (intakes, throttle bodies,thermostats, exhaust) Fuel system (pressure regulator, volume supply, pumps, injectors) regulation/metering system (wiring harness, ECU, sensor net) you can see the obvious overlapping parts of these systems...throttle body, pressure regulator...can also be put under regulation. The data supplied to the ECU is at many times, more important than what the ECU has in side of it. The ECU only supplies times impulses to the injectors...different data input gives different output.Larger injectors and higher fuel pressures can override a limited impulse range from the ECU. A carb system can be broken up the same way: air (throttle body, intakes, venturis) fuel ( jets, emulsion tubes, floats, pumps, accelerator pumps) regulation/metering..... there are so many parts of overlap and controls..in carbs...they are just more obvious. But the parralells are the same. You will learn more, by getting a few extra parts and tweeking/adjusting/disecting them...than any book I could reccomend. And it doesn't take very long. I hope this helps at all. Ray
germansupplyscott
Posts: 887
Joined: Fri Jul 20, 2001 12:01 am

Bus EFI Modifications

Post by germansupplyscott »

ray,

yes, it is helpful, as is reading the many notes that you and others post here. i am putting together a new motor for my van, and have all the necessaries for the stock system, good harness, sensors, injectors etc. i am interested in the HP gains you speak about in tuning the stock system, because this seems like more or less free, safe, relaible HP. i am building a camper motor, not a drag racer. on a different thread i was told to increase CR a bit - you mention this also. where do i start to research how this is done? i assume one needs to make the volume of the compression area smaller, but how is this accomplished correctly? i am building the motor myself, with some help, but i need to know what mods are needed MYSELF, because my engine builder helper does not know these particulars.

thanks,

scott lyons
ray greenwood
Posts: 1941
Joined: Thu Jul 19, 2001 12:01 am

Bus EFI Modifications

Post by ray greenwood »

Sorry it took so long to get back to you. There are handfuls of little tweeks. Some almost sound stupid...but are just not outwardly logical. I will need to know the specifics of the engine mechanicals, stroke, size, cam, valves....really just for a reference point. I will need a list of basic part #'s from you including distributor # and letter prefix...throttle body #...and note of any and all switches and wires attached to it...and throttle valve switch # if it has one. Wether it has a PCV fitting and hose on the air box, which type vacume advance and arm #, cyl head temp sensor #, itake air temp sensor #, does it use EGR, what # is on the aux. air regulator, what part # on the injector, what mass air unit # and what ECU #. I can look at your system here if I know all of these. Also what fuel press reg #...and see if there is a part # down between the injectors on the intake manifold casting. Include what you plan to use for exhaust system and ignition. Drop it to my personnal e-mail...I' give you a list of things we can possibly tweek and tune...and we can re-post that...if you want...so everyone else can play. jgreenwood@integracolor.com See ya Ray
ray greenwood
Posts: 1941
Joined: Thu Jul 19, 2001 12:01 am

Bus EFI Modifications

Post by ray greenwood »

Sorry I forgot to answer the compression question. The easiest and quickest way is to reduce the deck height of the piston at TDC by removing shims. You should dump the dished top pistons. The little dish seems insignifigant, but it was the difference between 7.8:1 and 8.0:1 in some of these engines. The 1.7 liter FI engine had domes which were the exact mirror of the dish piston. The difference between flat top and dome in that engine was 8.0:1 and 8.2:1. I reduced the shim thickness under the barrel a little bit to get a final of 8.33:1. Ask around for who is using what piston set. Watch your deck height and valve clearance!!!!. If a particular piston set gets you a little to high in compression...or a little too close to the valves...remember that the type 4 heads respond very well to good port/combustion chamber work. You should trial fit before you get your head work done so you can decide how many cc's of metal removal they can do...and get a better idea of final compression and shims. Ray
germansupplyscott
Posts: 887
Joined: Fri Jul 20, 2001 12:01 am

Bus EFI Modifications

Post by germansupplyscott »

oops, i bought the stock mahle pistons. they are dished. can CR be increased safely/properly while still using these pistons? they weren't cheap...
no matter how well you plan building an engine, things like this always seem to happen. i will email details soon.

scott
ray greenwood
Posts: 1941
Joined: Thu Jul 19, 2001 12:01 am

Bus EFI Modifications

Post by ray greenwood »

Yes, don't worry. Decreasing deck height will allow you to raise C.R. Have your heads cc'd before you do anything so you can calculate your comp. ratio. You will need to know your total valve lift before you start setting deck height. The little dish was mainly fine tuning by the factory. There is also enough metal in these pistons to allow cutting them flat...but I wouldn't do that.Anything can happen with more people handling them. It wouldn't be great to nick a ring land or something. If you have the cylinder spigots in the head flycut... to reduce the size of the combustion chambers...this will work also....and again valve clearance will come into play...but at that point...the dishes can sometimes give you a little clearance leeway. The domed pistons seem to give a little better charge mixing at least on FI engines. I have had engines with both flat and domes with an otherwise identical set-up and the domes appear to allow a little better tuning of the FI. The dish pistons appear to perform like the flat pistons...just a little lower compression. Ray
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