How much boost on stock engine?

[Dr.G]

i'm new to this board and i'm sure this may have been answered in a previous thread, but I wanted to ask everyones opinion on how much boost do you think one could safely run on a stock 1UZGE engine? I have heard anywhere between 8.5 to 15lbs. - does anyone really know for certain? I have a sc'd GS400 and currently I'm at 8.5lbs and i'm looking to increase but certainly don't want find out the hard way what my engine can handle!

 

[Lextreme II]

Hey Dr. G,

Have we met? I was at GA for a SELOC meet once last year. Anyway, are you running supercharger right now? If yes, which head unit and what is your pulley size for make that 8.5 psi? I have some info you might interested in.

 

[Dr.G]

Not sure if we met or not bud. the only seloc meet i was at last year was the big meet at Dave & Busters off of 85, then of course at NOPI. Anyhow, i'm running the RMM SC with a 2.87 pulley. My buddy Morris just had a custom cogged pulley setup fabricated (2.62 i think) and got 10.5lbs at 5500rpms before his belt broke the other night! They suspect he may actually be close to getting 12.5lbs with his setup now, but his tuner says a few more mods may take him to 15lbs. Again, all on stock internals, and this is what i wasn't sure about being possible or not? Any info you got would be greatly appreciated man!

 

[Lextreme II]

RMM SC uses Vortech V2 SQ S-Trim. 2.62" is the smallest pulley Vortech make for the V2. I am very sure the stock (unopen) should able to handle about 13 psi.. However, u will need more fuel. Tell us more about your system.

 

[Dr.G]

As already mentioned I have a 99 GS400 and running the RMM Vortech V2, 310cc RC-engineering injectors, stock fuel pump, SAFC2 and we just put on the new 2.87 pulley. Car is being tuned as we speak, the last run put down 372hp at 0.6 bar (8.7lbs) of boost, my tuner thinks he can probably get another 10hp out of it but it appears that i'm leaning out at the top end. So it looks like i'm already going to have to make the jump in injector size as well as upgrade my fuel pump.
The major issue that most all of the guys that I know that have the same supercharger kit on their GS4's are experiencing is belt slippage. So my buddy Morris just recently had a local shop custom fabricate cogged pulleys to resolve this issue and so far everything looks promising and I'm sure I'm soon to follow suit. He's scheduled to get dynoed either later on this week or next- we're anxious for the results! He says it's definitely a noticeable difference in the way the car pulls, boost comes alot sooner.

 

[Dr.G]

Another ? that comes to mind, is do you think I could get away with just upgrading my fuel pump and stay with the 310cc injectors for my current setup or do you think upgrading injectors as well is a must? what if I drop to the 2.62 pulley?

 

[Lextreme II]

You can get 2.62" pulley and get an adjustable fuel pressure regulator and Walboro Pump. Increase both might do the job. Cog? That is lots work and expensive. Is that mean all the pullies (Alternator, PS, Crank and so on) are cog now? Or Morris has a seperate pulley system?

 

[Dr.G]

Yep, a total of 3 cogged wheel (2 on the blower and power steering). Total cost was $950 for the measuring/making. I'm hoping since most of the leg work has already been done and there's essentially a template the price for those to follow will be lower, but now that there will be a demand I doubt it Here's a nice pic that he posted over on CL.

 

[Lextreme II]

Nice, but i think its over kill for the application. I would stay with 6 ribs belt and get 2.62". My cobra have 6 ribs and pumping about 17 psi.

 

[Dr.G]

Nice, but i think its over kill for the application. I would stay with 6 ribs belt and get 2.62". My cobra have 6 ribs and pumping about 17 psi.

it won't happen with our Millen kit and ribbed pulleys alone, everyone has the slippage issue to some degree with the smaller pulleys for some reason. It's due to the mechanical design of the setup (the blower is not structurally stable enough- it flexes forward under heavy load, thus causing the slipping and loss of boost) not to mention Millen designed and tested it originally to produce only 5.5lbs of boost on the GS400. We were going to just fabricate another bracket for the blower for more support, but the cogged wheels looks to be the more promising route.

 

[Lextreme II]

The problem is not really the flexing of the bracket. The problem with 1UZFE supercharging is that the crank pulley is too small and has the gear ratio disadvange. The 1UZFE Crank is 5.5" and even with 2.62" pully, it will max out at about 12 to 14 psi. Belt slippage is different from Belt coming off alignment. If you bracket flexes, then its common to have belt comes off alignment.

Currently we are designing a two stage crank pulley for the 1uzfe just for the supercharger application. It has the 5.5" crank pulley along with an extended piece that is about 7".

 

[staff]

How much boost?

UP to 15 lbs for short period of time without doing immediate major damage. Over 15 you will blow out the head gaskets.
I run a supercharged version as a daily driver at 8 lbs. and have found I can run 12 lbs. daily . without any major issues or problems. Over 12 you are looking to do some maintainence.

 

[JustenGT8]

I just wound the boost up from 6.5 psi to 10psi last night on my TT and no probs so far. Certainly no det which was my biggest concern. I'll know what hp it's laying down after this Sun.

 

[quadcam boat]

Intercooling has a major influence on the amount of boost you can use on a stocker.

 

[Red Supra]

With meth injection you can turn up the boost. Methanol can also be used as additional fuel.

 

[JustenGT8]

Well i got awy with 10psi easy...no hint of with 13 deg advance at full noise so i'll be sneaking some more timing in for sure. The car ran 270rwkw so not to shabby considering the tune and restrictive exhaust. The car will spike to 12psi on the road and still no hint of det so you should be able to run at least 12psi safely on stock internals with a conservative tune.

 

[Lextreme II]

Of all the uzfe engines. I think the 1998-2000 version of the 1uzfe is the one can handle most boost stock. Here are my reasoning:

1. 1UZFE have stronger rods
2. 2nd Generation 1uzfe have better piston design

I think 2uzfe and 3uzfe would be the worst of all the engines.