I've been working on the engine of Gymkhana Foxxy, VW 1.4i. As I've installed a 4.46 diff ratio and plan on using 2nd gear on events, I wanted to get some more low down and mid range torque. So I decided to work on the bottom-end first, will do the head later on. The stock motor with only 4-2-1 branch and 50mm free flow exhaust on Gotech management made 74kW and 136Nm. Then I added a 282 Estas cam and made 84kW and 140Nm. When I opened the motor I measured everything and found the CR to be 9.5 : 1 I decided to raise the compression to 10.83 : 1 to make better use of the cam. The work done on the bottom-end, Machined the pistons flat on top Decked the block Honed the cylinders New rings and bearings Knife-edged the crank Lightened the flywheel Balanced all the rotating parts Fitted a windage tray No head work done yet. Took the car for tuning and it made exactly the same power and torque! I really expected an improvement... [:^(] Had to play with the cam timing to get some more torque in the low to mid-range. Could the stock head be that much of a restriction at the moment that no matter what is done to the motor that it just won't make more power/torque? Would it help to put the stock cam back in to gain some torque in the low to mid-range, as I won't need to rev the thing as high anymore with the new gearbox? What else can be done to get more torque in the low to mid-range, except the obvious future head work?
maybe its detonating? what management has it for fuel and spark? did you check the compression , and the valves for leakdown?
http://www.gotech.co.za/index.html Seems to be a South African management system which makes sense as that's where the poster is from
Running Gotech EMS as already stated, it's a widely used in South Africa. Head has been pressure tested, so that's not leaking. It's not detonating, we've had the Knockbox on it while on the dyno, it actually makes best torque before detonation when timing is advanced.
Are you just looking at the peak numbers, or is there no difference in the whole curve? I'd have expected a CR increase to give you more bottom end power as well. Your post implies that you've considered that though. If you've looked at that, and tried adjusting cam timing, then I'd suggest you might have hit the limit of the engine's ability to flow air... either in the head, or somewhere else in the intake tract - throttle body / intake hoses / etc. As you already got another 15% peak power, you could be at the limits of the intake side. Have you been using a wideband probe to make sure the mixture is about right? Sounds like the exhaust *shouldn't* be the problem if it's good quality kit. We don't get the same brands over here... Stuff to think about: Did it need any more fuel when remapped for the higher compression? If not, it's got no more air going through it. Mixture before/after? Do you have any before/after compression tests? Are the new rings bedded in properly, do you think? Again, that could reduce the air being sucked in. I wouldn't go putting the stock cam back in just yet... the cam change got you 10kw, after all, and you're making pretty good power for a 1.4 litre 8 valve.
The whole curve stayed the same with the cam on 0deg (properly dialed in) The cam timing was adjusted to gain some torque in the low & midrange, with the sacrifice of some top-end torque. The car is mainly used between low & midrange. At this stage I'm suspecting the breathing capability of the head. But what bothers me is that inorder to have good low & midrange torque you don't want big open ports which suites top-end better. Wideband probe and knockbox was used throughout the dyno tunning session, no issues there. Exhaust *shouldn't* be a problem, but I'm going to experiment in anycase. Good point, AFR's remained pretty much the same after the rebuild, only had to to be tweaked here and there, but nothing significant. Unfortunately not, I don't really understand the significance of doing this especially with the high duration cam. Could you please explain the significance of doing this test? Yes, I ran the motor with some 3deg retarded ignition timing for about 3 hours of high load and eventually high load and rpm. The reasoning wrt the stock cam, is that the motor still made more low & midrange torque when it was completely stock, although peak torque & power increased on the modded motor.
MhVW If you do not mind, What method did you use to work out the compression? Is this the 75PS (55kW)@5000rpm 16v engine we have in the European Fox? If so that engine is quoted at 10.5:1 compression. If the static compression is increased then this should be reflected in a compression test providing you have data for similar before pulling apart the engine. I believe this is what Mike H was suggesting. Do you have the plots for the engine before/after that we can see?
Increasing the CR shouldn't increase the amount of air flowing through, it just means you extract more work from the same trapped volume. In answer the OP, as toyotec has said, could the engine have been 10.5, and you upped it to 10.83 - and unsurprisingly seen no noticeable difference. You did change a fair few other things, could any gain be lost due to other changes or in test to test variation? This suggests that you can still go further with your CR, you want the torque to be just levelling out as you advance into det.
I'll bow to your better knowledge on that one. I was thinking it should sook harder, but actually the size of the vacuum is still the same, so why should it. Good point. There could still be some gains from looking at the inlet tract though - e.g. by porting out the throttle body. VW engines don't always measure out at the book CR figure, in my limited experience, and Doktor Danster's far greater experience.
I agree, but not by a point. Unless there is a 16v 1.4 with 9.5:1 CR designed for a market with low RON fuel. There are a lot of sides to measuring CR that can be easily missed as I have shown in this article.
Pretty sure the OP is talking about the small block 1.4 8v SOHC engine. Maybe like the 1.4 ABD found in mk3 Golfs, or it could be the later incarnation which has slight differences that came in 6N polos. The ABD engine is like a stroked 1.3 GT 3F coded engine, but lacks the compression of the GT engine, and the multipoint efi too. But as the OP states it has an aftermarket ecu, then he really needs to clarify what engine it is. His previous posts in other threads lead me to the above conclusion.
The engine is a 1.4 8V SOHC, as mentioned. Engine code AGY. I'm not sure if this engine has been used in other VW's in Europe, but in South Africa it has been doing service in the Citi Golf (late RSA Mk1), in stock form it is equipped with the MP9 fuel injection engine management system as we around here know it. Fox, is the late version of the Mk1 Jetta as the Citi Golf is the late version of the Mk1 Golf, thanx to VWSA. My Fox originally had a 1300 carb GY engine code. I fitted the AGY almost a year ago, using an ADY intake and throttle body using the Gotech management.
I did measure the compression ratio properly by cc'ing the combustion chamber, piston dish, head gasket thickness & bore, deck height, etc. The stock CR came to 9.5:1, this was then increased by machining the pistons flat top and decking the block to come to the CR of 10.83:1 The CR of 10.83 was chosen with consideration of the specs cam and the dynamic CR.
Pear shaped? New one on me! If my memory serves me right then the best heads for flow are from the hydraulic tappit mk2 or mk3 polo with the rectangular inlet ports, although, as said above, I've never seen a pear shaped inlet ported head so that statement may well be incorrect I take it the head is cross flow? Have you thought about itb's seems you are running an ems
These photo's are not from my head but similar one. VW 8V u-flow 1.4i hydraulic tappet head. As can be seen the intake port has a pear shape. The small top section of the port is for the fuel injector to inject the fuel into the port.
Hmm, that is unexpected to see pics of a head like that. That style of head is found on the big block VWs, not the small blocks I had guessed at earlier in the thread. What is the bore and stroke of this 1.4 engine?
