My latest exhaust mod, a.k.a. Turbo Q45

[ScottJackson]

The T70 should spool up relatively well. A cheaper option would be a Holset HX-40 or H1C. Prob have a bit large turbine side, but would be a good way to get going cheaply and see how it all works.

[Unnatural1]

Has anyone thought about or maybe even tried propane injection? From what I've read it seems like another good way to ward off detonation. I know the turbo Mitsubishi guys are very into it. I remember reading about one owner of a 3000GT VR4 (or Turbo Stealth can't remember which) that was able to run 22-25psi on premium pump gas on the street. Just curious.
Modified by Unnatural1 at 9:01 PM 3/30/2007

[qsiguy]

Can you explain a "Hobbs" switch. I assume it's just a pressure switch that turns on at a set PSI? I can do that quite easily so if that's what you are talking about I'll do that for sure. I'm starting with the low boost and I'll get it working with that before I start trying to increase it. Once the system is in mods will be reletively easy.

Scott, I agree on the Holset. I had previously thought it wouldn't work well but after doing much reading up on turbos and properly sizing them I know it's a good match. I actually bid on an HX35 the other day but didn't win I found the compressor map and got some specs for the Hx35 and it's a great match. If you can find one from the early 90's Dodge trucks they don't have the internal wastegate so you can add it externally. That's what I was going to do. I'm still watching for another one for a good price. They are good quality but you have to be careful buying a used one.

[ScottJackson]

yes, a Hobbs switch is a small pressure switch. They don't typically flow much current so it's best to use one to turn on the relay which in turn feeds the alky pump. The internal gated Holsets can be used also. The diesel wastegate is set at a higher psi than most of us would go (around 15-20psi). So you can just hook up an external gate and not worry about it. The HY35 has a single scroll 9cm exhaust housing and spools faster than the HX35 with split scroll 12cm housing. However, the HY also has a little smaller compressor wheel so it won't feed as much hp as the HX. It's true that many of the used HX and HY 35s are pretty worn out. Still, rebuilding one isn't difficult so long as the fans are good and the shaft is good. Just have to mark them so you don't throw off balance upon re-assembly.

[Rex]

IIRC, they're forged. I could be wrong.

I'm pretty sure the VH45DE pistons are not forged, but I don't knonw that it'll be an issue unless you try to go too far past 5psi

I'm shopping around for an M30, Miata, Z32, E34, E30, Seville, Fleetwood... anything else, really...

I know where there's a Z32 'vert for sale ... reasonably priced and all.

[WDRacing]

I'm pretty sure the VH45DE pistons are not forged, but I don't knonw that it'll be an issue unless you try to go too far past 5psi

I know where there's a Z32 'vert for sale ... reasonably priced and all.

The pistons can be made of almost anything, from the lowest carbon cast units to high alloy forged aluminum. As long as you have no detonation you'll be fairly safe up to about double the stock whp. Alot of times quite a bit more. Fortunatly, the VH45 is a 4 valve head design which is far superior to any 2 or 3 valve pushrod head. The head design itself wards off detonation. Eliminating knock is THE most important thing when running boost. I'll sacrifice torque and power all day if it means running with a larger safety margin. And since none of us can afford to run C16 all day, we're either swapping low CR pistons or looking into detonation resistant injection systems.

Has anyone thought about or maybe even tried propane injection? From what I've read it seems like another good way to ward off detonation. I know the turbo Mitsubishi guys are very into it. I remember reading about one owner of a 3000GT VR4 (or Turbo Stealth can't remember which) that was able to run 22-25psi on premium pump gas on the street. Just curious.

Modified by Unnatural1 at 9:01 PM 3/30/2007

Propane is usually 114 octane. I've done ALOT of research into using it for subinjection. Unfortunately very few people are using this method so I have to use some speculation. I know there are some guys over on LS1Tech running nitrous with propane on the wet side instead of pump gas with very good results. The propane will distribute itself 100% throughout the combustion chamber, it won't pool anywhere in the intake system and it's the cheapest source aside from water. I was going to install a DIY kit into my 240, but tossed a rod through the block prior to my experiment. If the tank is mounted in the trunk and secured VERY well it's just as safe as running without it. Since the pump gas in the fuel tank will ignite and explode long before the propane will.

The thing I can't find is anything related to tuning. And since the kit can't be made variable, unless you use a system that will rapid fire a solenoid. But this burns out solenoids pretty quick. Nitrous Express makes a system that would work if you wanted to go variable. I was only looking at a one or two stage setup using one or two solenoids at preset boost levels.

The tuning would have to be done via EGT, since you'd be mixing 2 fuels relying on AFR's would be to difficult. It can be done by adding propane until you get the egt's into a safe level. At $20 a month for a refill it's definitly worth playing with. I know some cab companies have used propane injection in their high mileage cars in order to run 87 octane.

Can you explain a "Hobbs" switch. I assume it's just a pressure switch that turns on at a set PSI? I can do that quite easily so if that's what you are talking about I'll do that for sure. I'm starting with the low boost and I'll get it working with that before I start trying to increase it. Once the system is in mods will be reletively easy.

.

Here's a good link that explains the Hobbs switch in detail. They only show the 10-400 psi switch, but they are available for low boost applications. NAPA carries them as well as hundreds of websites.

Hobbs Switch

Having it turn on a relay or solenoid valve is the way I'd go.

WD

[qsiguy]

Ok, never heard it called a "Hobbs" switch. I have pressure and vacuum switches in stock. I have some 7-8 PSI pressure switches that we use in one of our machines. It might even be adjustable I'll have to look again. I have other models as well, I'll have to see if one of them is suitable. If not we have dozens of suppliers for stuff like that.