lobuxracer

iTrader: (2)

I did some homework on the ISF and GSF fuel systems after I realized I did a true DS on reconnecting my fuel lines after the valve lash inspection. Believe it or not, the engine will idle if you connect the fuel lines for direct injection backwards. It will soon set DTCs and it will shut down in short order, it will also not run above idle (it will die like whacking open the slides on a bike engine with oversized carburetors), but it will actually run. It took me too long to figure out I'd made a stupid mistake.

Anyway, after this debacle, I took a look at the GSF sitting next to the ISF and found Lexus re-engineered the fuel system on the GSF (and of course, RCF). The fuel pulsation dampers are integrated into the HPFPs where they are external and separate on the ISF, and they've remove the return entirely - the ISF has a "spill valve" on the HPFR that bleeds back into the fuel tank almost like the old school port injection systems where the GSF and RCF have a pair of opposing check valves on the HPFP to maintain the correct pressure in the DI fuel rail instead of depending on a spill valve and return line. Ingenious, for sure, and eliminates an extra fuel line and the consequent connections necessary to support a fuel return to the tank. It would not surprise me if it were possible to adapt the newer fuel pumps to the ISF and simplify fuel delivery too.

At any rate, if you find yourself in a spot where you have removed both the fuel lines from the LHD driver's side and can't remember which goes where, I guarantee you they are backwards if the engine won't run above idle. AMHIK.

isfvss

I think cost and why bother comes to mind when swapping fuel systems, ( don't get me wrong) but very good information cheers.

jdmSW20

iTrader: (12)

good info, I was wondering the extent of the tweaks done to the blue top 2UR

lobuxracer

iTrader: (2)

You won't see me doing a swap unless it's swapping the whole thing into the ISF. Totally not worth the time and effort of converting when used HPFPs are available on eBay for $400 US.

MileHIFcar

Here is what I found real quick:

Compression ratio UP intake and exhaust port improvement (intake: a high flow rate and high tumble)
Cam profile improvement (valve lift UP)
Operating range expansion (performance, both of fuel consumption, Atkinson cycle of)
Crank pin size reduction, counter weight reduction high-strength forged material, the large end hole size reduction
Titanating
Shape improved (oil hitting improvement)
Change Material
Water cooling + air cooling (circuit racing corresponding strengthening) tube length, tube diameter, optimized larger diameter surge tank volume (φ83 ← φ76) Semi dual of (exhaust interference reduction)
New D 4S (high fuel pressure of, spray shape improvement) with One way clutch
Valve lift (mm) / Material
Fuel supply system
13.0 / Ti

https://www.clublexus.com/forums/is-...-blue-top.html

supersonic

iTrader: (2)

see this is what i wanted to know. i googled for a while and couldnt find the answer. so saying the cylinder heads were refined is accurate for the "new" engine then? or was there more done for that added power?

flowrider

iTrader: (9)

See this post:

https://www.clublexus.com/forums/is-...lue-top-2.html

Lou