still kinda new to forums,.. just wondering if people have boosted an is250 RWD.... its most likely been done , but i want to know how quick will it make it... is it worth spending the 2-3k doing a good turbo setup? or the car itself isnt good for turbo? .. just looking for some advice here as ive been debating turbo charging it.. really wish i baught an is350.. but couldnt afford it at the time..

any idea how much a stock is250 can handle for boost? im curious as to what id need to upgrade if i was to drop a turbo in and say push 6-10 lbs

 

I have a supercharger (getting rebuilt, then will be installed) on my is250. LMS Kit.

Here we go again though, i'll try to be brief:

No one runs a turbo on these cars that i know of, but a few have supercharged them. Why no turbo? I dont know enough about boosting to answer why one and not the other. Search, you'll probably find it.

You're looking at a minimum of $4k for a used supercharger kit to be bought and installed. New they were around $5500-6000, but no one produces a kit anymore. I believe a place in Cali will put one together still for about that price.

Boost: Max of ~7psi. Horsepower gains are (arguably, but dyno results shown by Pepos from Greece) ~70whp. You're looking at coming very close to an is350 if you have all the bolt ons (PPE headers (~$800), full exhaust (~$1000-1700) and the SC ($$$)).

I wont get into why thats the limitation, but please search for HKS350's thread, mikellucci's threads or search for "supercharger" and you'll find plenty.

Upgrading? You could do meth/water injection to cool temperatures, and mapecu to take more control of your ecu. But from what i've gathered, the >$1k to get and run mapecu wont yield much greater results.

Lastly, I will post before and after gains once i have mine installed (probably in about 2-3 weeks, Procharger hasnt started the rebuild yet, but have received it). My before will be with current setup: Fujita intake, ppe headers & hfc, and joez racing exhaust. After will be with ~5psi or 7psi, depending on what i choose to run, belt size wise.


EDIT: Also, people will forever tell you on this forum to "trade up for a 350 or an F". If thats an option, go for that first, of course. Wasnt an option for me (uninstall/reinstall of all my upgrades would cost a fortune). People that negate this idea should keep in mind that a full authentic wald kit runs >$3000 + paint, BBK $2000+, brand name wheels run from ~$2000-4500+, so making this not an option due to monetary, dollar per horsepower terms should be carefully worded in my opinion. And again, if you're doing it to be the fastest car around, of course you're in the wrong car.

 

I would argue that the decision the car isn't fast enough for you ought get made before you invest $8000 in non-speed mods that aren't easily moved to another car



Otherwise, yeah, it's not worth doing at all compared to just getting a 350.

You won't get 7 psi on a 250 safely without using a piggyback ECU (which is what the guy in Greece had to do- the car ran frighteningly lean before that). On a stock ECU you're looking at 5 psi (which is what the LMS kit was originally designed to do, and gives you 40-50 more hp)

At that point, especially going with the piggyback, plus the relevant bolt ons (headers and full exhaust) you'll have spent about double the price difference from a 250 to a 350 and still be making less power than a stock 350.



Nobody has done a turbo because as explained above, you can't make much boost on the car anyway, and it's both more expensive, complex, and takes up more scarce engine-bay room to do so.

A couple guys have toyed with the idea of running a rear-mount STS style turbo but nobody has actually done so to my knowledge and I expect results would be similarly underwhelming as all other forced induction applications on the 2IS have been compared to just trading it in for the faster version of the same car from the factory.


If you're curious why it's so limited do a search, plenty of threads on it... the short version:

12:1 compression ratio, complex piston design, even more complex fueling and ECU systems, and unknown overall strength of the cylinders and block.

 

I wish i would have known i was going all out on my car before i started so i would have traded for a 350, trust me! I started the serious modding (>$1k mods) last October, and here i am, at the end of the line with a SC.... haha


I dont consider myself, or anyone on the forum to contain or speak the bottom line truths for performance on these cars, but for what its worth, Pepos in Greece told me anything under 7.5psi will be able to run on the stock ecu, with meth injection, as long as you never mash the gas for extended time periods. Is "not mashing on the gas for extended time periods" very vague and not a clear line in the sand before damage could occur? Yes. Am i wary of doing 7psi? Yes. The kit came with a pully for ~5psi and i'll probably run that until i get water/meth injection (it's already 100+ degrees daily here in Houston...) and then i may swap to a smaller pulley for ~7psi.

 

personally with all the $ you've got into this already I'd recommend throwing a MAPECU3 on there rather than the water/meth system... it's simpler, gives you more control, and should let you run 7ish psi pretty confidently.

My understanding was it was the MAPECU3 that fixed his crazy-lean fuel trims at high boost (and HKS350 similarly used a piggyback, not water/meth, to successfully run those boost levels albeit on a 350) , but I suppose asking him directly would be best.

 

Very true, and i most likely will add mapecu3 at some point in the near future, just to be "complete"

Mapecu3 did correct his lean-ness, correct. From a PM with him in these regards though:

"The meth kit provides safety in long runs with the pedal on the floor, it reduces temeratures a lot in the combustion chambers so i would say go for it.
It also gives you a bonus of 9 BHP at high rpm.
just say to the controller of the meth kit to start spraying at 3.3 psi.
Never go above 7.5 psi, up to there our engine's knock sensors do a perfect job without having any need for a piggy.
I would not recomend to go above 7.5 even with a piggy though.
But up to 7.5 you are perfectly safe along with the meth kit."

I've gathered that mapecu will correct a/f ratios but other than that will not gain much more (power wise, at least). Not knowing "how dangerous" it is to run without it is my grey area, and everyone's, i suppose. Other past and current boosted guys have told me water/meth is ideal due to my location (100+ ambient air temps all summer long in Houston), and it seems the more logical first step after boosting opposed to mapecu that is quite a bit more expensive for little more than piece of mind while flooring it.

I'm being another guinea pig and i plan to share everything with the forums.

 

thanks for the info/advice guys , this car is my DD so i wouldnt want to have constant problems or anything limiting me as a DD it...i will look into superchargers tho, havent even given them much thought tbh. ive always been a fan of turbos, and i thought perhaps this was a good motor for one (not knowing what i do now).

if i could trade this car in i would for a 350 or isf, but i cant..burried myself in payments for a few years... but i will try and make the best of the 250 rwd ?

 

fixed for you

 

I'm trying to make my 250 faster too I only have the joe z intake planning on getting a greddy exhaust I was wondering if a iss forge will fit on my 08 is250

 

forget it..just trade it for 350...

 

I know this is a Lexus forum. If really want boost why don't you trade in your vehicle for a boosted vehicle that cost less than the IS250