Sevenman's TVR (was SAAB) Blog

November 14, 2012

TVR Power dyno run

Filed under: TVR — Administrator @ 9:50 pm

As I was curious about how much power my Tamora was making, I took it to TVR Power for a dyno run.

I dropped the car off with Jason to get it strapped down, and then wandered towards Coventry to find some food (fish and chips) and got back in time for the runs to start.

A video of the Dyno Run is here

Depending on how the graph is smoothed, it made either 309 or 314 bhp at the wheels at 7000 rpm and a max torque of 248 lbft at ~ 5500 rpm. The wheel figure seems to be good for a stock 3.6, and compared favourably with other 3.6 plots on the system. A de-cat, bigger injectors and a custom map made the same peak power, but with a small amount of extra torque throughout.

There was a slight stutter around 6000 rpm which shows as a gap in the plot vs. rpm, but does not show in power vs. wheel speed.

Jason and Dom attributed this to the injectors running past their max which can happen in certain conditions and said it was nothing to worry about. When this happens the injector demand goes past max and back to zero. Given it was a relatively cool November day and air pressure was slightly above average, this could be possible.

The air/fuel ratio sat around 14 for the run, which is apparently standard. Apparently making it richer does not produce more power. This may be seen as a bit high for a power run, I will have to check this but they didn’t seem worried.

I am reasonably content that the engine is running as it should. It uses no oil or water, pulls well, and peak power is what it should be.

After the dyno work was done, Wayne changed the front pads for new DS2500 supplied to TVR Power by AP Racing. These are standard fit for the front. The original pads also seemed to be DS2500, but apprently were quite glazed. This could explain the rear-bias issues. And mean that the fitment of an adjustable bias valve was a waste of money.

Subsequent testing has suggested that the new pads have improved the brake issue, but I need some proper track testing to be sure.

Ready to go

Ready to go

Power / Torque vs. RPM

Power / Torque vs. RPM

Including air/fuel ratio

Old pad

New pad

Old pad (top), New pad (bottom)

Not as shiny as some TVRs

Not as clean as some TVRs

Center Gravity

Filed under: TVR — Administrator @ 9:32 pm

A busy day for the TVR planned – a suspension health check at Center Gravity followed by a trip to TVR Power for some rolling road time.

The health check is not a full setup, but a series of checks / tests to see what state a car is in and decide what to do next.

An early start up the M6 and M42 but it is an easy drive and I arrive around 08:30 for opening time.

After a coffee and a chat Chris takes the car for a test drive with me in the passenger seat. This cover a range of road types, speeds and manouevres. The bumpy B road is quite hard work, and a rear tyre rubs on the wheel arch on one bumpy bit. The car seems to ‘thrust straight’ under power and manages 27mph on the calibration roundabout before the front starts to run wide. Chris thinks that, with a refined setup, it could manage a little more. The turn-in is described as ‘rip your face off’, which I take to mean fairly aggressive.

After the drive tyre temperatures are taken (even across the tyres), pressures checked (Chris thinks the rears should go up by 2 psi) and it goes on a damper test rig which works through a range of amplitudes and frequencies. The knocking sound which we had also heard on a cobbled road turns out to be a corner of the bonnet (later fixed with a stick foam pad).

Damper test video

All the dampers seem to have a good response that is matched across the car. I am given some printouts from the computer with these plots. The test rig also measures the car’s weight as 1078 kg.

The car goes up on the ramp and the ride heights are measured off the outriggers. These are:

Front Driver’s side = 160mm    Front Passenger side = 157 mm

Rear Driver’s side  = 171 mm     Rear Passenger side  = 171 mm

Chris noted that the track rod ends were different lengths and questioned whether the rack was centred. Adjustment was 18mm passenger side and 31mm drivers side. He also noted what I had seen when the tyres were changed, the inside of the passenger side wheel has been ‘machined’, as if it has rubbed on steering lock.

Of concern was the rear damper travel when the suspension was laden. In terms of piston travel before the bump stop (which is 5cm and quite soft) there was only 15mm on the driver’s side and 20mm on the passenger side, and the piston was shiny, so that travel is being used. The front suspension had much more piston visible, and it was clear that it was not reaching the bump stop as there was a short dirty section of piston.

All bushes looked ok. It was noted that the rear drive shaft gaitors were rubbing on the anti-roll bar when the suspension compressed.

Damper settings on the Gaz Gold Pros were inspected. Chris measures settings from fully-stiff, whereas I had been setting from soft (as others seem to do). Settings were:

Front Driver’s side = 7 from full stiff (of 21)    Front Passenger side = 9 to full stiff (of 20)

Rear Driver’s side  = 10 from full stiff (of 20) Rear Passenger side  = 9 to full stiff (of 18)

Chris suggests that damper adjusters should be exercised through their range occasionally. The fronts are ok, but the rears start leaking oil from the adjuster seals when this happens. It stops after adjustment, but shouldn’t be happening.

Chris felt that the rear was bit too stiffly damped compared to the front. I had upped the rear damping slightly before going on the road trip to help avoid tyre rubbing issues. Chris backed the rear dampers off by a couple of clicks.

The wheelbase was measured as 8mm longer on the passenger side than the driver’s side. This could be due to adjustments made to cope with an off-centre steering rack.

The car was put on corner weight scales, and weighed 1124 kg with a full tank of fuel. If I rempved the fire extniguisher and bits in the glove box it would probably be 1120 kg. Not bad for an aircon-equipped car fully fuelled.

The car had a 50/50 front/back distribution when loaded with driver weight, but the cross-balance was a bit off (46.8%), and could be improved.

Rear springs rates were checked and found to be 325 lb / inch. They should be 350 and we discussed changing them to 375. That should help with running out of suspension travel. Chris was also going to check with Gaz to see if there was a short-bodied damper that could be used, although it was noted that the setup already allows the wheel to touch the wheel arch in some conditions so more compression would not be beneficial.

I left at 11:30 for TVR Power. It had been a long and busy session: we set off for the test drive at 08:50, so have got 3.5 hrs of time for the £146 cost, and it has been informative.

Chris promises to send out the report soon, and we can make a plan for getting the car how I want it.

On the ramp


More checking

Rear wheels on damper test rig, taking things out of the boot.


November 7, 2012

Extra brake work planned

Filed under: TVR — Administrator @ 10:20 am

Had a chat with Dom at TVR Power this morning.

Following the rolling road session they should be able to fit some new brake pads to the front. These will be the AP racing supplied CP6600D55-DS2500. I guess the extra numbers just show the fitment as well as DS2500 being the compound.

I used DS2500 on the Saab a couple of times and they were very good. They never faded on track despite the high power, fairly high weight, and relatively small disks of the Saab. The TVR has more power, a lot less weight and large brake disks, so they should be fine for hard track driving. In addition, they work fine year round and from cold.

Discussing the brakes Dom also mentioned his thoughts on getting it on a 4-wheel brake tester. Apparently there is one near them. He thought the split should be 75/25 front/rear when static. If I can find the piston diameters for the front/rear brakes then I should be able to calculate the natural bias excluding the valve. The rear has smaller disks (but not by much) and smaller single-piston callipers, but I need to find the exact details.

November 1, 2012

Ford not very helpful. Brittania Rescue and Gaz are helpful

Filed under: TVR — Administrator @ 2:10 pm

I have been trying to get an answer to my question on the specification of the Ford brake proportioning valve that is fitted to Speed 6 TVRs as standard.

When I posted this in October it looked good – Ford had acknowledged my request for information and it had been passed to their technical team.

However, when the letter arrived I was disappointed. It basically said that they couldn’t provide any information on the brake proportioning concern as the vehicle was not a Ford and that I should contact the manufacturer.

Via e-mail I pointed out to them that it was a Ford part, and that I could not contact TVR as they went out of business 6 years ago. And that my question wasn’t about a a brake proportioning concern but was a specific question about a Ford component that could be answered with a single number, for example 0.4 (fraction of pressure passed through).

When I received another phone call things looked good. The matter had been passed to Ford Technical again, and this time they would be sending some information.

A few days later the information arrived. Sadly it was of no use. I had given them the part number and the information that I needed, and they sent me a page from some Ford manual about how much extra weight should be placed over the rear axle for testing load-sensing proportioning valves.

I don’t understand how anybody could have read my question and sent me this as an answer.

I phoned the number provided on the latter for the Ford Customer Relation Centre and after being transferred twice I spoke to the person who sent me the letter. She suggested I contact the Technical Information Centre directly and gave me a phone number.

Thankfully I checked before calling it, as it is a £1 / minute phone number. She didn’t mention that. I did however find an address to which questions can be sent, so I have sent them a letter which makes the question very clear. We will see what happens.

Gaz shocks were very helpful. In advance of the trip to Center Gravity I wanted to check the spring rates in the kits fitted to TVR. The answer came back within an hour of 400 lb/inch front and 350 lb/inch rear. I asked via e-mail how much new springs were, providing a phone number, and they called me back soon after.

New springs are a very reasonable £25 + VAT / corner (so £30) and delivery is £11.25.

While their standard kit is 400 / 350, some people go up to 450 / 375. Apparently the dampers fitted by TVR to the Tamora / T350 are a bit short relative to the springs used, and this effectively gave the spring some pre-load. This maintained ride height but at the expense of a ‘chattery’ ride.

The Gaz setup does not do this, so should could a more compliant ride in the initial part of the travel. The damping I am running (12/10) at the moment could be turned down a little if stiffer springs were fitted.

Some additional information was provided. Apparently the front springs are mounted very nearly straight, and the rear springs are at a significant angle. This means that the spring rate for the front may go from 400 to 375 effective, but the rear could lose nearly 40% of its spring rate. Therefore some people just put a 400 on the rear to match the front.

This is all useful information to discuss with Chris at Center Gravity.

In addition, Britannia Rescue were very helpful when I had a question about my policy.

If only Ford were helpful as well

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