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Engine Specific Info and Questions => IDI Engine => Topic started by: rabbid79 on May 11, 2006, 11:43:13 pm
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Hello All,
I've been hanging around this forum for quite a few months and I feel that there is a wealth of information and wisdom here not found anywhere else. I'm sure you folks can answer the title of my post better than anyone. This discussion concerns the differences between the 1.5L and the Naturally Aspirated 1.6L. Why is there so little interest in the 1.5? Is the N/A 1.6 THAT much better? I'm sure that the sheer number of 1.6s produced compared to 1.5s has something to do with its popularity. Plus, because they're older, there are simply fewer 1.5s left.
So, how do the two engines compare mechanically? Here's what I know about the 1.6:
>Obviously larger in displacement due to stroke
>Larger piston pins
>Larger head bolts
>Hydraulic heads on newer 1.6s
Here are some things I don't know about either:
>Forged pistons? As far as I know the 1.5's are cast. Are the N/A 1.6's cast or forged?
>Forged crankshafts and connecting rods? Which engine has which?
>Cam differences?
>Block differences?
>Head differences (other than head bolt size) Does the 1.6 flow better? Does it have bigger valves?
>Pump head size differences?
I'm considering building a 1.5 turbo and feel that some of the 1.5's shortcomings (such as head bolt size, lack of oil squirters, etc.) can be be addressed. I don't consider the 1.5's stroke to be a shortcoming and intend to leave it at 80 mm. I'd just like to know why I've never seen a 1.5 modified to the same extent as a 1.6. I know, most people would tell me to modify a 1.6 or 1.6TD instead, but that's just it. I want to do something different, and that's why I'd like to use the 1.5. For some reason, you just don't see hot 1.5s. What else am I missing? Don't get me wrong, I think the 1.6 is a good motor. I'm not trying to stir up a hornet's nest, I'm just looking for answers. Thanks.
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The 1.6 is better because it has 4HP MORE than the 1.5! :lol:
48HP (for the 1.5) -Vs- 52HP (for the 1.6). Yea! One more lawnmower's worth of extra power!
Seriously though, the 1.5 is just as good as the 1.6. There are simply not many 1.5s left is more likely the reason you don't see them around.
Also, I've been told be a VERY reputable VW Diesel Parts dealer that 1.5 pistons are extremely difficult to find new anymore. That making rebuilding one not a real viable option.
BTW, I have a 1.5 list on EBay right now. 8)
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8064505057
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I think you're on the right track with the popularity of the 1.6 being due to it's relative age and production numbers more than anything. The biggest turn-off for 1.5's is basically the head bolts. With the 11mm bolts they tend to go through head gaskets like.....well I'll save the analogies for later. Regardless, it is a concern in terms of reliability and most of the time when an engine is replaced nobody bothers to concern themselves with the 1.5.
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not to mention they never came turbo.
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look at how much torque the 1.6 na makes over the 1.5,,and it makes more at a lower rpm...... i think its almost 15 foot pounds...thats what you feel,,,some of the power loss is in the pump,cam, etc,a lot of little things that add up
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So far so good. It's been 24 hours and so far no one has given me a reason not to try it. :D
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So far so good. It's been 24 hours and so far no one has given me a reason not to try it. :D
other than engineering enhancements done to the 1.6 that the 1.5 obviously does not have such as head bolt upgrade as mentioned before.
I would rather have the improved engine, but would settle with the older one if I had to.
I wonder if a 1.5 block could be bored out to handle 1.6 stock pistons? I'm guessing it would be a bad idea due to added stress on the crank, rods, block... etc, but 1.5 pistons are rare.
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Ok, good, this is exactly where I'm trying to go with this.
Head Bolts: Why wouldn't Raceware or ARP head bolts be able to make up for the flimsy 11mm factory bolts? And while we're at it, what about head gaskets. Since 1.5s and 1.6s have the same bore, wouldn't 1.6 TD head gaskets work? Ok, here's an issue. The head gasket bolt holes would be larger on the 1.6 TD head gasket. What kind of issues would this cause? And finally, most people want to upgrade to metal headgaskets anyway. I'm assuming there isn't one made for the 1.5. Does anyone have experience having a custom one made. Copper or something?
Pistons: Why go with the 1.6 pistons? Are they superior in some way? I know the turbo pistons have the oil squirter cutouts. But are the 1.6 pistons forged where the 1.5s are not? BTW, there's a set of KS 1.5 pistons (stock size) on eBay for $150. What do people know about KS?
Thanks for your replies.
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i cant remember,didnt the 1.5 have a cast crank??i remember mine(1.5) that was in my 80,i didnt like the powerband,you really had to rev it alot to get a little,i swapped to a 1.6 when it blew up+5 speed... it seemed like the 1.6/gti trans had good power,and way torquier,,,,besides,, i guess you said 1.5 parts are a little hard to find,another use then for a stock 1.6,,,now if you are rebuilding a stocker 1.5,then yea do it,but to me,unless its allyou have,find somethin bigger maybe??im not tryin to axe your idea,just sayin its alot of work to do an engine,think about it first before diving in :wink:
heh toobad
http://forums.vwvortex.com/zerothread?id=2496239
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So I'm hearing weak block near the headbolts, and possibly a cast crank. Neither of these things bode well for a modified 1.5. I presume that the N/A 1.6 has a forged crank? Can anyone confirm or deny that? Were there any special circumstances on the block(s) that broke near the headbolts? How often have you seen that? The headbolt holes didn't have any oil in them that would cause them to break when they were torqued down or anything? FYI, some of my inspiration comes from the fact that VW built a 160 HP version of this motor back in the '70s when they were developing it. Unfortunately, I don't have any specific details.
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So I'm hearing weak block near the headbolts, and possibly a cast crank. Neither of these things bode well for a modified 1.5. I presume that the N/A 1.6 has a forged crank? Can anyone confirm or deny that? Were there any special circumstances on the block(s) that broke near the headbolts? How often have you seen that? The headbolt holes didn't have any oil in them that would cause them to break when they were torqued down or anything? FYI, some of my inspiration comes from the fact that VW built a 160 HP version of this motor back in the '70s when they were developing it. Unfortunately, I don't have any specific details.
160 hp? :shock: from a 1.5 liter engine??? Couldn't be diesel. Diesel technology back then was less than great. Even squeezing 160hp out of a gasoline 1.5 litre engine would be hard without a turbo, if not impossible. Using the stronger diesel parts, and a whole lot of fuel could possibly do it though :)
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Well, I was reading from the SAE paper concerning the development and evolution of the 1.5 diesel from the 1.5 gas. They did use turbo charging to achieve 160 HP, but it doesn't say specifically that it was the diesel that made that much power. Instead it says "the basic powerplant". You could be right. Perhaps it was the gas version that made that much power. Just the same, since the diesel was derived from the gas, it's good to know that the block/crank/rods/head were able to tolerate that much power - even if only for a while.
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The gas engines are stout. I've turbocharged several of them and they've always held up quite well. Making 160hp from a 1.5 (gas engine) actually isn't all that tough with a turbo strapped to the back.
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Head Bolts: Why wouldn't Raceware or ARP head bolts be able to make up for the flimsy 11mm factory bolts?
1.6 engines have angle torque bolts that stretch when you tighten them. 1.5s don't. Not sure if you can get angle torque bolts for the 1.5, but it would definately help as they tend to go through head gaskets at a rate of 1 per 75,000km.
And while we're at it, what about head gaskets. Since 1.5s and 1.6s have the same bore, wouldn't 1.6 TD head gaskets work? Ok, here's an issue. The head gasket bolt holes would be larger on the 1.6 TD head gasket. What kind of issues would this cause?
1.5 engines were all solid lifter, most 1.6s were hydraulic. You can't use a hydraulic head gasket on a solid lifter engine. The fibre gaskets were pretty much junk anyway and on the turbos they are just plain funny. Imagine putting 10 psi of boost into a 23/1 compression ratio 1.6 diesel engine, and all that is holding it all in there is a metal rim with a fibre gasket behind it? The head gaskets didn't last very long.
And finally, most people want to upgrade to metal headgaskets anyway. I'm assuming there isn't one made for the 1.5. Does anyone have experience having a custom one made. Copper or something?
The metal head gasket lowers compression slightly. All metal head gaskets are hydraulic, so they wouldn't fit on a 1.5 engine anyway.
Just the same, since the diesel was derived from the gas, it's good to know that the block/crank/rods/head were able to tolerate that much power - even if only for a while.
The 1.5 diesel was derived from the gas engine, the 1.6 wasn't (it was a completely new engine). This is another reason to avoid the 1.5s. Gas to diesel conversions are notoriously bad (remember the Chevette diesel?)
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The 1.5's can use the same 11mm stretch bolts that are available for gas engines. Alternatively, they make head studs for gas engines. Those should also improve durability.
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Good news! I contacted Bildon, and they said that they have, or can get, 11 mm Raceware or ARP head studs (I'm not sure which). I think I'm going to go ahead on this project. The worst that can happen is I'll blow the little motor. Since they're basically being given away for free, I'll just get another one, or I'll take all the mods and put them on a 1.6.
I want to track the evolution of this thing. First I want to get a couple of bone stock quarter-mile runs. Then I'll put on the GTD nozzles, air dam, lightweight flywheel, synthetic oil, and adjust the fueling. I'll do a few more runs to check the improvement. Then I'll install the turbo, exhaust, and windage tray and run again. One of the last things I'll do is add an intercooler or water injection, install high strength head stus, and increase the boost.
Depending on how this projects goes, and if I think there's still room to grow, I'll add an oil cooler, larger radiator, Ti valve components, lower compression ratio, thermal coatings, forged crank, etc. I hope she holds together...
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hehehehehe, turbo on a 1.5.......better figure out how to cool the pistons. I think you can use the 1.9 metal head gasket if you block the extra oil hole somehow, might try that. I am very interested to see how long a 1.5 will last with all these performance mods. They used to crack their engine blocks and mix their coolant and oil together after about 100K in a rabbit in normal 48hp stock configuration.
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I think a definite must, would be coating the tops of the pistons with at least ceramic. That would definitely help keep the pistons from melting. As for the head... coat that too if you want to turbo it. Your motor will be happy, and you will be happy for not blowing it. Also, open up the exhaust, and get yourself an EGT gauge at the very least.
As Chrissev said, you should be more worried about cooking the motor than blowing the head gasket.
Alternatively, I would suggest supercharging it. Check this out:
http://vwdiesel.net/phpBB/viewtopic.php?t=3643&highlight=supercharge
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Before I do anything too exotic, I just want to get the thing put together and running. I'm hoping the engine will prove durable enough to justify spending more money on it later. If and when I do pull the head, I'll probably do just like you said and have it thermal coated. I'll also put in sodium filled exhaust valves if they're available. I'd also consider titanium if somebody makes them.
Obviously, cost is a concern, and I think it would be cool to pull the stock pistons, have them thermal coated, and put them right back in. I would LOVE not to have to pull the motor and tear it apart to do this.
I have considered supercharging it, but I'm concerned about parasitic power loss from the S/C. This small amount of power this little motor can make needs to go to the flywheel instead of turning a S/C. I also don't think the S/C is capable of making the kind of boost I hope to eventually have.
An EGT gauge will be among my first purchases. I won't run it any harder than the EGTs will allow without the thermal coatings.
The principle idea is to use the high-RPM characteristics of this motor to make HP. 100 ft./lb. at 6000 RPM is still 115 HP. Hopefully this isn't too much to ask of it.