I want to create a “poor-man’*” HV insert for my 1998 LeSabre Series II L36…
…because I think $200 for a modification I might be able to do for $40 is crazy. (The $40 is for a junker UIM I picked up from Ed Morad)
On this site (under Tech Info) you can find a tech report for the HV insert:
I really would have liked if easyperformance had tested the HV insert without all the other mods on the test car, as I suspect the ER rockers synergized greatly. When I get around to my on-car testing, the only other performance mods I will likely have at that time will be two other low-cost items: 180° drilled thermostat (about $30 including coolant), and a home-ported LIM (about $40, also using a junker from Ed Morad):
(ER rockers and a Powerlog v2 are on the list for this car, but not before the UIM/LIM work is done and tested).
We know the stock L36 has its torque peak at 4000 rpm, though looking at the stock dyno, it’* pretty flat on torque starting below 3000 rpm:
I would like to increase torque (of course), but also shift the peak torque up to somewhere around 4200 to 4300 rpm. The reason for this is that I feel this engine “drops off” at the tops of the gears, even with the stock shift points of 5700 rpm (1-2) and 5400 rpm (2-3).
I’d also like, as with the LIM porting, to do something that any stock, normally aspirated L36 owner could do on a tight budget.
Doing some calculations on this site with a 231 cubic inch v6:
I come up with:
A peak tq rpm of 3300 results in an optimum 25.45 in intake length, 1.44 sqin port
A peak tq rpm of 3900 results in an optimum 21.54 in intake length, 1.71 sqin port
A peak tq rpm of 4500 results in an optimum 18.67 in intake length, 1.96 sqin port
I measure the stock, "ugly" L36 LIM-to-head port at about 1.4 sqin, and I estimate the stock overall runner length (from intake valve seat to top of UIM plastic runner) at 12 to 13 inches. Assuming second order pressure wave (i.e., actual runner length half of optimum), this puts the stock LIM port optimized for ~3200 rpm and the overall runner length optimized for ~3800 rpm. This matches the stock dyno quite well.
So, what if I ported the LIM ports to about 1.7 sqin (optimized for about 4000 rpm), and shortened the plastic UIM runners by about 3 inches (total intake runner length then 9 to 10 inches, optimized for second order pressure wave at about 4400 rpm)? I would expect the stock torque curve to shift “rightward” by about 200 to 300 rpm…and hopefully “upward” as well.
(My understanding is that the HV insert runners are considerably shorter than what I'm talking about doing. While that surely shifts the torque peak even higher, it likely causes low-end losses that I don’t want, so I’m being less “aggressive” than the actual high-ticket item. Besides, if you shift the torque peak too
high, you'll be forced to increase shift points, and then this wouldn't be cheap anymore 'cuase you'd need a tuner or a tuned PCM)
I’m too cheap to run dynos for you people, and as willwren predicted, the GTech sucked so bad it nearly pulled me out of my seat. So my plan is to optimize the VE table using a DHP PowrTuner (supposed to arrive this week), comparing “before and after” VE tables to see if I got any VE changes, and in what rpm range(*). If anyone else has any ideas for low-to-no-cost methods for quantifying these mods, I’m all ears.
Based on my quicky calculations, the UIM plenum volume on the Series 2 L36 is already massively oversized at over 150% compared with displacement—even correcting for the volume displaced by the plastic runner insert as-is—so the slight increase in plenum volume I’ll experience when cutting away part of the plastic runners shouldn’t require any correction.
I do not think I’ll need any intake mods to see results with the modified UIM; however, I do have a gutted airbox with K&N standing by, just in case.
Process (with pictures) will be documented starting with my next post, as this one’* getting too long…