I am pretty confident that with ~$500 in fuel system upgrades like a 190lph walbro pump, an adjustable pressure regulator and new injectors coupled with a larger GT28R/GT30R MHI 14B/16G sized compressor pumping through a nice large intercooler with C16, E85/98 or Meth + 93 pump gas achieving a reliable 240whp should not be a problem if you maintain strict maintainence.

You can do a built bottom end in a GD for less than $1500, that with ~$500 in sleeves would see you safely past 300whp.

There are in fact lower compression pistons, Mahle or Wiseco make pistons on request in addition to the 9.8:1CRs they have off the shelf..


Wiseco L15A 73mm 9.8:1 Pistons: Evasive Motorsports | PH: 626.336.3400 Mon-Fri, 9am-6pm PST


Boost is not the limit, boost is but one of the dials you can turn in tuning.

The GT25 being too small and inefficient where our engines use them is a big issue, because @ 12psi flowing only ~22-25lbs/min they are already blowing hot air, and high IATs along with the rigid engine management provided by HKS on a high compression engine are what causes detonation. It looks like lean detonation too.

The information from the service manual that Lyon posted in my tech thread suggests the factory fuel system wiring, lines, fittings, make it tough for the already undersized pump to keep flow up when overall fuel pressure exceeds 63psi, so 52psi BFP + 11psi Boost.


Fuel Pump Head vs Flow vs Voltage | Blowerworks.biz


MKIV.COM - Fuel Pump Upgrade Guide

For 11psi boost:

https://www.fitfreak.net/forums/fit-...er-meth-7.html

Nothing has visibly melted in that picture BTW, that is just a snapped conrod.. Unless the dome of the piston melted and he did not show a picture of that. But there would likely be slag from the piston melting on the wrist pin and conrod its self were that the case.

There are a couple great points, but there is so much misinformation in this thread I don't even know where to start. From the carnage pics it looks more like one of the conrod bolts yielded after he bent the rod a bit under predetonation and that led to the ensuing failure..

IATs, AFRs, compression, fuel quality and timing make up the rest of the equation. Boost is ambiguous in this equation when you don't have the other numbers.

Those stouter conrods and a larger compressor would allow him to make more power at the same boost on a more conservative tune.

Not only would you have a less streetable power curve (torque specifically) N/A, because of the cam and other VE mods needed but to even reach your power band you would have to wind to the moon to make 220whp. The piston speeds, the friction that comes with it on the rotating assembly and the demands on supporting systems like the water and oil pumps, accesories, valvetrain and drivetrain components shifting at the stratospheric redline required to churn out 200whp+ from a 1.5L.

This would be far more detrimental to longevity than boosting the engine and maintaining the stock redline to create the same amount of power.

Sorry for the essay but it is frustrating to see so many half truths, speculation and whole lies stated so confidently as fact.

 

Ive seen a stock K20a2 run 20 pounds of boost with c16 racing fuel. The engine was thrashed and tuned and ran the quarter mile 30 times or more with no problems except for the pipe blew off a few times where it was clamped but most of the piping was welded. We check the plugs a few times at the track and richen it up a little but had more traction problems than engine problems. You cant run more than 6 psi with pump fuel unless you lower the compression but if you use the right fuel and the right tune, I can see it running 10-14 pounds of boost easy. You also have to remember that a stock cam is different than a boosted cam. Stock cams dont have a lot of overlap to bleed psi off and because a boosted engine needs overlap to help scavenging to help it breath better at higher rpms its limited to how much power it can make safely.

 

i appreciate the essay. helps people not in the know (like me) build knowledge.

i used melted as a figure of speach since this is not an engine specific forum and most people are not engine builders or mathematicians.

most people equate boost pressure to the limiting point of this motor. (everyone assumes they are using a t25 since no one is running custom kits yet.)

 

Sorry I didn't mean to single out your post but I am glad that it was a helpful in some capacity.

It's still hard to use boost as a limit, even on a T25, because there are more than a few different configurations under the designation T25, GT25 and GT25R. Those are all basically the same compressor with different turbines and turbine housings. These things change the compressor maps efficiency islands as well as where in those islands we can use.

 

indeed i know where your coming from.

i have contacted eagle for sleeving my l15 block and i think i will release a suprise motor that will test the limits of the flow capability of the head.

porting seems to be a big no no on this motor however due to material thicknesses.

i did take a spare head and have it x rayed to see if that was possible.