Sam's build thread

[Sirocco20348]

Hi Sam and Gary,

Can I ask something about injector flow differences and what are acceptable tolerances of difference?

I watched a video from a professional company that designs and manufacturers injector cleaning machines (I'll have to find it again) but they were quite upfront with saying that any difference in flow between injectors was unacceptable. Basically to scrap them and source new ones.

USRT also advertise 'flow matched' injectors where injectors are individually tested and paired with others of identical flow rate.

The only reason I ask this is that I remember when mine were cleaned and I noticed the vials of fluid were quite different but the cleaner guy said that it was acceptable!?! I don't have exact difference values but it was more than a couple of mm difference. One looked a good 10mm difference.

In my situation I think it was a big deal as the injectors were running at their limit, so they needed to be in perfect working order for max performance.

Sorry for the hijack.

[Sydneykid]

It varies, Bosch Motorsport Injectors are within 1%, I've seen new production injectors vary around 10% even after cleaning. For the 4 cylinder Production Cars I usually grab 10 or more injectors and pick out the closest 4. Then use them in the engine as per the previous post (highest flowing in #1 etc).


Cheers
Gary

[seangti]

Hi Sam, re oils, my TSI Jetta will run oil temp of 120c just cruising down the highway, 110-114 sitting in traffic. Was up to 125c in summer. I saw a mechanic about my concerns and he checked it out and found that to be quite normal/no issue. My concern was oil breaking down at such temps, so he checked with Castrol about boiling temps for the VW spec stuff, which is rated to ~148 degrees. That gives me piece of mind to not be too bothered about using thicker oils for high temp applications and will run the spec'd stuff.

And given the rate the TSI's drink oil, it's almost always got new oil in it anyway, lol

[sambb]

Yeah its crazy how hot (water and oil) they run modern engines. What I don't get, after having it hammered into me all my car life that oil burn will lower your octane rating leading to knock, is how these ultra lean, high comp boosted engines running at searing temps just around town, that guzzle a litre of oil per 1000km aren't rattling themselves to bits.

[sambb]

RE my possible fuelling issue, for now its just a bottle of Liqui Moly injector clean and some new plugs. I'll read them after a few thousand km's and see what they look like, knowing that they haven't possibly been switched to different cylinders like the last set. I suppose to be properly scientific about it I should turn the water injection off so that it doesn't potentially affect the appearance of the plugs.
My local injector cleaner guy has just sold up and took his machine with him. I used to be able to park up there, take the injectors out and have then done and then put them back in myself and drive off. I spoke to the porsche guys at PR Technology and they said they send theirs away to Pacific EFI but that'll have me off the road for ages. I suppose I can just do some digging in the misfire and timing pull logs and hopefully if they point to a cylinder that coincides with a dodgy looking plug, that will be worth a stab to swap in a new injector.

Sirocco20348 Ive read through your posts re the injector seal and cup leaks. Ever since my Bosch EV14's went in, there is fuel weep in that area. My logs show no air leaks and spraying around with WD40 at vacuum hasn't revealed any vacuum leaks in those areas so I think it may be the top seal seating into the fuel rail. Either way it'll all come out for a spruce up when I make my mind up for which inlet manifold i'll go with. Have you killed off your leaks there with the new cups? They sealed ok into the mani without any issues?

[Sydneykid]

Hi Sam, re oils, my TSI Jetta will run oil temp of 120c just cruising down the highway, 110-114 sitting in traffic. Was up to 125c in summer. I saw a mechanic about my concerns and he checked it out and found that to be quite normal/no issue. My concern was oil breaking down at such temps, so he checked with Castrol about boiling temps for the VW spec stuff, which is rated to ~148 degrees. That gives me piece of mind to not be too bothered about using thicker oils for high temp applications and will run the spec'd stuff.

And given the rate the TSI's drink oil, it's almost always got new oil in it anyway, lol

Yeah its crazy how hot (water and oil) they run modern engines. What I don't get, after having it hammered into me all my car life that oil burn will lower your octane rating leading to knock, is how these ultra lean, high comp boosted engines running at searing temps just around town, that guzzle a litre of oil per 1000km aren't rattling themselves to bits.

In no particular order;

In my family we are up to VW #5, 2 x MK6 Golfs (one GTi & one TFSI), 2 x Mk7 Golfs (one GTi & one TSI) and 1 X MK5 Polo GTi. I have not seen oil temp over 105 degrees in any of them, that's in heavy traffic on 40 degrees days, a good workout up MtVictoria etc.

FWIW none of them have ever needed oil between services ie; less than 1/2 litre over a year.

Euro spec oil is designed to be consumed, so it is possible that it doesn't affect the octane rating like the older, non Euro spec oil used to. A question for me to ask the oil chemist next time I drop off a sample for testing.


Cheers
Gary

[Sirocco20348]

In regards to the injector cups, I was seeing leaks at high psi boost leak testing. At 20-22psi it would bubble away with soapy water on the outer edge of the cup and the loss of pressure was quicker than usual. (Not super fast like a split pipe thou). The leak wouldn't bubble at lower psi pressures (e.g 12psi and below).

How much effect these leaks had on performance, possibly minimal but still metered air leaving the engine. I am very happy with the power my car is producing now.

If you are buying a new intake plenum you might aswell get the billet cups, they are $100.

[sambb]

Yeah its pretty interesting the tricks they play with oils. I was reading in Racecar Engineering an article about direct injected engine oils. Studies into the Mini coopers in the UK Cup series that were destroying ring lands due to standard racing oils being high in Zinc. Fuel at lower loads was collecting around the ring lands. The high Zinc in the oils was reacting with cylinder wall oil that was getting past the low tension rings. This was causing the production of octane lowering compounds causing local pockets of very lean and low octane fuel that was then knocking under high load/ low speed conditions. They changed to calciums and sulfates I think to replace the Zincs and now the engines in that series are holding together. Different engines, different oils I guess.

[sambb]

I'm looking at going to either a Golf mk4 gti or mk 1 TT mani, as they appear to have bigger more uniform plenums and it looks like slightly longer runners too but I could e wrong about that as they will work with my SEAT Sport intercooler. The plan is to replace the cups for billet ones like you did, add a few more vacuum take off points and also a pair of water injection points on the outside (radiator face) of the plenum to accept water injection jets. 1 jet between/facing the runners of cyl 1 and 2 and another at 3 and 4 to mimic the BMW M4 GTS setup, where pairs of cylinders share a jet. Yes the BMW arrangement is a centre fed plenum and ours is side fed but that's got to give better cylinder distribution than going with a large single point jet further up the tract.

[Sydneykid]

I'm looking at going to either a Golf mk4 gti or mk 1 TT mani, as they appear to have bigger more uniform plenums and it looks like slightly longer runners too but I could e wrong about that as they will work with my SEAT Sport intercooler.

I have yet to find an inlet manifold/plenum that works better on a turbo engine just because it has longer runners. Even airflow across the cylinders is far more relevant. I'm not a fan of larger plenums (post throttle body) on circuit race cars as they dull the throttle response. Increasing the distance/volume of air between the throttle body and inlet valves simply adds delay in the throttle open/throttle closed time frame. That's why GTR's (designed from scratch as a circuit race car) have the multiple throttle bodies close to the inlet valves, to improve the throttle response.

If I was building a VW turbo charged circuit race car I'd be trying to find the inlet and plenum off a Pulsar GTiR and adapt it to fit.




Cheers
Gary