Hey guys here's a question for you. In a BBC 454 what would the pro's and con's be of a twin turbo setup vs. a single turbo setup. Thanks in advance.

 

The general rule of thumb I've read is that twins tend to come on at lower boost (two smaller turbos) but that if you are going for high HP single turbos are more efficient. It seems most of the turbo charged race guys use single turbos.

 

It's basically personal choice whether you want single or twins because when properly sized there is no benefit in spool time, efficiency, or HP output of either setup.

The rule of thumb is single has a simple cold side, but complex hot side. And twins have a simple hot side, but complex cold side also twins require double everything (double the wastegates, double the oil lines, double the drains, etc.). Other than that it's up to you.

Smaller twin turbos are easier for the DIY guys to find at the JY cause they came on 4 banger cars as most vehicles didn't come with a turbo large enough to support a V8 in a single application.

Other than that I know there are some more points that can be made on single vs twins that has come up in many topics before, but it all boils down to personal choice and what you have available to you.

 

What about cost? I would assume one bigger turbo would cost less than doubling up on everything.

 

Again it depends on what you can get your hands on and what you prefer.

A Master Power T70 (which has been used pretty extensively on a 5.0) can be had for less than $700 new and $500 used. Whereas I bought both my T3's freshly rebuilt for $400 with internal gates. Add in the cost of external wastegates (if you want to go that route on twins) and either setup would have probably cost the same for my engine and goal. Now if you're going with all brand new parts the twins will probably end up costing more than an appropriately sized single depending on which type or brand of turbos you buy.

Note my research has only been done for a 5.0 V8 not the BBC the original thread starter has inquired about. Therefore I'm not sure what a properly sized twin or single would be for his setup. I've read of people using twin T70's on setups that big (these may or may not be the appropriate size for that engine so don't take it as gospel) and for the price of the Master Power T70's I would think two of those and two wastegates would be about the same price as an appropriately sized large single. Another thing to take into consideration with larger singles is getting that appropriately sized larger downpipe out of the engine bay (if that is a concern). With two smaller twins the two downpipes might fit better in a tight engine bay than a large single downpipe (which can also be split if needed, but could add more complexity).

Again there are different pros and cons for each, but it's primarily up to the person installing the turbo which pro outweighs which con...again basically personal preference.

One more thing I forgot to mention is power potential will play a huge role in proper turbo selection.

 

Things I would consider would be:
Overall look
cost
piping..Twins would probably fit easier on my BBC Chevelle. Smaller turbos, 3" DP instead of 5" but the fab time and planning would take a little more time.

W